The orientated cathode in a proton exchange membrane fuel cell was simulated and compared with a random cathode using a microstructure lattice model. The differences between catalyst utilization and electrode performance were studied. Transport and electrochemical reactions in the model catalyst layer were calculated. The orientated cathode performed better than the traditional random cathode and was explained by variations of the oxygen levels, the over potential and the reaction rate across the catalyst layer with cell current density. Additionally, we examined the electrode performance at different thicknesses. Unlike the traditional random cathode, a thinner orientated cathode performed better.

The precursor powder of CaVO₃ was prepared by sol-gel method using vanadium pentoxide, calcium nitrate, citric acid, and oxalic acid as raw materials. The target product CaVO₃ was obtained by calcining the precursor powder in argon atmosphere at 1000 ℃. In order to determine the appropriate calcination temperature, thermal stability of the precursor powder was tested. The target product CaVO₃ was characterized by Fourier transform infrared (FTIR) spectrometry, thermogravimetry (TG), X-ray diffraction (XRD), and conductivity. In addition, the properties for oxygen reduction reaction (ORR) were also investigated, and the results showed that the electron transfer number of ORR on the modified electrode was 1.5-1.7, which indicating that ORR was a two-electron process.

Cross-linked porous carbon nanofiber networks were successfully prepared by electrospinning followed by preoxidation and carbonization using low-cost melamine and polyacrylonitrile (PAN) as precursors. The structures and morphologies of the nanofiber networks were investigated using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and N₂ adsorption/desorption. The carbon fibers had an interconnected nanofibrous morphology with a well-developed porous structure including micropores, mesopores and macropores, high-level nitrogen doping (up to 14.3%), and a small average diameter (about 89 nm). Without activation, the carbon nanofibers had a high specific capacitance of 194 F·g^-1 at a current density of 0.05 A·g^-1. Cycling experiments showed that the specific capacitance retained approximately 99.2% of the initial capacitance after 1000 cycles at a current density of 2 A·g^-1, indicating an excellent electrochemical performance.

In this study, graphite oxide was prepared from natural graphite powder using a modified Hummers method. Well-dispersed Pt nanoparticles were synthesized on reduced graphene oxide (RGO) via a simple one-step chemical reduction method in ethylene glycol (EG) by simultaneous reduction of graphene oxide (GO) and chloroplatinic acid. The microstructure, composition, and morphology of the synthesized materials were characterized with Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). It is shown that the GO was reduced to RGO, and the Pt nanoparticles with an average particle size of 2.3 nm were well dispersed on the surface of RGO. The catalytic performance of the catalysts for methanol oxidation was investigated by cyclic voltammetry and amperometric method, which indicated that Pt/RGO catalyst had higher electrocatalytic activity and stability for the oxidation of methanol than the Pt/C and Pt/CNT catalysts. The I_f/I_b of Pt/RGO reached 1.3, which was 2.2 and 1.9 times as high as those of Pt/C and Pt/CNT catalysts, respectively, revealing that Pt/RGO had high poisoning tolerance to the CO_ad intermediate species produced in the methanol oxidation reaction.

We fabricated highly ordered ZnO nanosheet arrays on ITO substrates by adding KCl and ethylenediamine(EDA) through potentiostatic deposition, then produced a hierarchical structure of ZnO nanorods on the nanosheets by using secondary electrodeposition. Shell-core Sb₂S₃/ZnO nanostructures were prepared from ZnO nanosheets and ZnO nanorods on nanosheets by chemical bath deposition. The nanostructures were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and their photoelectrochemical properties were investigated using ultraviolet-visible spectroscopy (UV-Vis) and photocurrent measurements. The shell-core Sb₂S₃/ZnO based on the hierarchical micronanostructure had higher photocurrent than did the shell-core Sb₂S₃/ZnO nanosheets. A hybrid solar cell was fabricated with a P3HT/Sb₂S₃/ZnO film as the photoactive layer. The P3HT/Sb₂S₃/ZnO hierarchical electrode exhibited an energy conversion efficiency as high as 0.81%.

Surface modification of semiconductor materials is an effective way to improve their photocatalysis and photo-conversion activities. Bare and V-modified α-Fe₂O₃ photoelectrode materials were prepared using hydrothermal, chemical bath deposition and heat treatment approaches. Their physicochemical and photoelectrochemical (PEC) properties were then investigated with X-ray diffractometry (XRD), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), voltammetry, and electrochemical AC impedance spectroscopy (EIS) techniques. The existence of FeVO₄ was indicated by its characteristic X-ray diffractometry patterns, while no significant red shifts in the photoabsorption edge were detected in UV-Vis diffuse reflectance spectroscopy spectra. With V-modified and bare Fe₂O₃ serving as a photoanode, photoelectrochemical measurements were carried out for water splitting in 1 molmol·L^-1 NaOH (pH 13.6). The enhancement of α-Fe₂O₃ photoelectrochemical activities through V-modification was indicated by significantly increased photocurrents and decreased photocharge-recombination probability. By measuring electrochemical AC impedance spectroscopy spectra, pseudo-first-order rate constants for the charge transfer at the illuminated electrode/solution interface were estimated. The rate constant for V-modification of the Fe₂O₃ electrode was higher than that of the bare Fe₂O₃ electrode. Improved interfacial charge transfer kinetics through V-modification is responsible for the enhanced photoelectrochemical activities of α-Fe₂O₃. The interfacial photocharge transfer and recombination processes and their properties are discussed with a semiconductor energy band model constructed for the electrode system.

A novel dendritic carbazole derivative (BTCPh) was designed and synthesized by simple chemical route. Its homopolymer and copolymer of BTCPh with (3, 4-ethoxylene dioxythiophene) (EDOT) were electrochemically synthesized and characterized. Cyclic voltammetry and UV-Vis spectroscopy were used to investigate the spectroelectrochemical and electrochromic properties of the two polymers. The copolymer P(BTCPh-EDOT) film revealed richer electrochromic color than that of the homopolymer PBTCPh film (yellow, green, blue, and grey) and showed five different colors (orange, green, brown-green, blue, and grey) under various potentials, which may be attributed to the introduction of the EDOT unit generating more doped states of the polymer, resulting in richer colors. Electrochromic switching tests indicated that both polymers possess good optical contrast and fast switching times. These properties show promise for potential applications on smart windows and displays.

Poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) proton exchange membranes were synthesized via single-step grafting sulfobetaine methacrylate (SBMA) onto PVDF. Benzoyl peroxide (BPO) was the initiator, and the PVDF was initially modified by tetramethylammonium hydroxide (TMAH) in the liquid phase. Microstructure morphologies and sulfur distributions in the membrane were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX), respectively. The PVDF formed C=C double bonds following dehydrofluorination by TMAH. SBMA was grafted onto the modified PVDF backbones, forming a homogeneous sulfur distribution in the interior and exterior of the membrane. Proton conductivities and methanol permeabilities of PVDF-g-PSBMA membranes increased with the increasing of the TMAH mass fraction in methanol. When the mass fraction was 20%, the proton conductivity of the membrane was 0.0892 S·cm^-1 at 20 ℃, and the methanol permeability was 4.04 × 10^-7 cm²·s^-1 at ambient temperature, respectively. The membrane exhibited good thermal stability up to 270 ℃, as verified by thermogravimetric analysis (TGA). With this membrane, the peak power density of a direct methanol fuel cell (DMFC) was 17.06 mW·cm^-2.

Multi-walled carbon nanotubes (MWCNTs) were modified with the long-chain polymer poly (diallyldimethylammonium chloride) (PDDA) and used as support for Pt nanoparticles (NPs). Pt/PDDA/ MWCNTs electrocatalysts were prepared by electrostatic adsorption of Pt NPs on the PDDA/MWCNTs support. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterization revealed that the Pt NPs were well dispersed on the PDDA/MWCNTs support, with an average diameter of ~3.6 nm. Thermo gravimetric analysis showed that the loading of Pt was 36%(w). Rotating disk electrode (RDE) measurements showed that the Pt/PDDA/MWCNTs catalyst had excellent electrocatalytic activity for oxygen reduction in alkaline medium. Compared with commercial Pt/C (40%(w)), the Pt/PDDA/MWCNTs catalyst exhibited a positive shift of 30 mV for the oxygen reduction onset and half-wave potential. Kinetics study further confirmed the significantly enhanced oxygen reduction activity of the Pt/PDDA/MWCNTs catalyst in the alkaline medium.

Cyclic voltammetry and chronoamperometry have been used to investigate the mechanism of gold electrodeposition on the n-Si(111) electrode surface from a citrate bath, which had successfully applied to directly electroplate a dense gold film on the silicon surface. The results show that Au electrodeposition on the n-type silicon surface is an irreversible process, and the nucleation overpotential reaches 250 mV. According to Cottrell equation, the diffusion coefficient (D) is calculated to be (1.81 ± 0.14) × 10^-4 cm₂·s^-1. The Scharifker-Hills (SH) model was used to analyze the experimental data. Agreement between the fitting curves and the theoretical curves confirms that the nucleation process of Au electrodeposition on the n-type silicon surface follows the progressive nucleation mechanism with three-dimensional growth under diffusion control. To further confirm the progressive nucleation mechanism, scanning electron microscopy (SEM) was used to observe the nucleation and growth of Au deposits at the initial stage of electrodeposition. The SEM results show that the morphology and density of the Au deposits are affected by the electrochemical deposition potential and time.

A nanocomposite composed of N-doped mesoporous carbon material (NDMPC) and carboxymethylated chitosan (CMCH) was fabricated by mechanical co-mixing and used as an enzyme matrix. A novel glucose/O₂ enzymatic biofuel cell was fabricated with a Nafion ion-exchange membrane consisting of a laccase (Lac)-entrapped biocathode and glucose oxidase-incorporated bioanode. Enzyme electrodes were prepared by the dripping coat and air-dried method. The performance of the laccase-based electrode as a biocathode in a fuel cell and an oxygen electro-chemical sensor was characterized by cyclic voltammetry in combination with the rotating disk electrode technique, linear scanning voltammetry (LSV), and chronoamperometry. UV-Vis spectrometry and graphite furnace atomic absorption spectroscopy were used to investigate the configuration of enzyme molecules on the surface of electrode and to evaluate the enzyme loading of the matrix on the electrode interface. The results from the experiments showed that the laccasebased cathode displayed direct electron transfer between the active centre in laccase (T₁) and the conductive matrix without any external electron mediators (apparent electron transfer rate 0.013 s^-1). A minor overpotential for oxygen reduction (150 mV) was also observed. Through further comparison of the intra-molecule electron relay rate (1000 s^-1), substrate turnover frequency (0.023 s^-1), and previous enzyme-conductive matrix electron transfer rate, quantitative analysis showed that the latter was the rate-determining step in the whole catalytic cycle of the oxygen reduction reaction. This laccase-based electrode as an oxygen electrochemical sensor for detecting oxygen showed a low detection limit (0.04 μmol·dm^-3), high sensitivity (12.1 μA·μmol^-1·dm³), and affinity for oxygen (K_M = 8.2 μmol·dm^-3). This laccase-based cathode also had advantages such as excellent reproducibility, long-term usability, thermal stability, and pH endurance. The results for the fabricated biofuel cell showed an open circuit voltage of 0.38 V and a maximal energy output density of 19.2 μW·cm^-2, maintaining greater than 60% of the initial value even after continuous work for 3 weeks under optimal conditions.

By introducing a new method of solution preparation, systems of equimolar mixing cationic/anionic surfactants with dissymmetric lengths of alkyl tails were investigated using light scattering, rheology, and freezing-fracture transmission electron microscopy (FF-TEM) measurements, in which the cation was docosyltrimethylammobium bromide (C₂₂TABr) and the anions were sodium alkylcarboxylates (C_n-1COONa, n = 4, 6, 8, 10, 12, 14, 16). The results showed that spherical micelles were favored when the cationic/anionic surfactants had highly dissymmetric length tails (C22/n4). With decreasing dissymmetry of the alkyl tail lengths, the aggregates transformed to rod-like micelles, worm-like micelles, and finally vesicles. In the vesicle-formed cases, the size of the aggregate considerably increased with decreasing dissymmetry of the alkyl tail lengths. By analyzing the mechanism of aggregation, the geometry of the cation/anion pair is thought to determine the morphology and the transition of aggregates.

The cuboid layered 0.6Li₂MnO₃-0.4LiNi_0.5Mn_0.5O₂ cobalt-free lithium-rich solid-solution cathode material was synthesized by a facile quick co-precipitation method. The prepared material was characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP) spectroscopy, field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical measurements. It was found that the as-prepared material has a typical hexagonal α-NaFeO₂ layered structure with R·\overline 3 $ m space group, and the chemical composition of this material is similar to the corresponding target material. SEM and TEM images reveal that the cuboid structures are assembled from nanoparticles with particle sizes of 40-200 nm. A possible formation mechanism of this cuboid aggregation is proposed. The electrochemical tests (in the voltage range 2.0-4.8 V vs Li/Li⁺) indicate that the as-prepared material exhibits excellent rate capability. It delivers approximately 243 and 143 mAh·g^-1 corresponding to 0.1C and 10C, respectively. Moreover, the asprepared material has good cycling stability even after high rate measurement, delivering a high capacity retention of 90.7% after 72 cycles at 0.5C. This co-precipitation approach, which has facile operation processes and good results, is a economic technique that could facilitate the application of Li-rich cathode on a large scale.

Li₃V₂(PO₄)₃ and its triple-cation-doped counterpart Li_2.85Na_0.15V_1.9Al_0.1(PO₄)_2.9F_0.1 were prepared by a conventional sol-gel method. The effect of Na-Al-F co-doping on the physicochemical properties, especially the electrochemical performance of Li₃V₂(PO₄)₃, were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), Raman spectroscopy, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), galvanostatic charge/discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). It was found that combined with surface coating from residual carbon, this triple-cation co-doping stabilizes the crystalline structure of Li₃V₂(PO₄)₃, suppresses secondary particle agglomeration, and improves the electric conductivity. Moreover, reversible deinsertion/insertion of the third lithium ion at deeper charge/discharge is enabled by such doping. As a consequence, the practical electrochemical performance of Li₃V₂(PO₄)₃ is significantly improved. The specific capacity of the doped material at a low rate of 1/9C is 172 mAh·g^-1 and it maintains 115 mAh·g^-1 at a rate of 14C, while the specific capacities of the undoped sample at 1/9C and 6C are only 141 and 98 mAh·g^-1, respectively. After 300 cycles at 1C rate, the doped material has a capacity of 118 mAh·g^-1, which is 32.6% higher than that of the undoped counterpart. It is also noteworthy that the multiplateau discharge curve of Li₃V₂(PO₄)₃ transforms to a slope-like curve, indicating the possibility of a different lithium intercalation mechanism after this co-doping.

Diamond-shaped carbon-coated CoCO₃ (CoCO₃/C) particles were prepared by a simple hydrothermal method, and carbon coating was realized using glucose as the carbon source. This study focuses on the electrochemical performance of CoCO₃/C as an anode material. Its surface morphology and crystal lattice structure were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The content and structure of the carbon coating layer were further investigated by the thermogravimetry-differential thermal analysis (TG-DTA) technique and Raman spectroscopy. The pore size distribution was characterized using the Barrett-Joyner-Halenda (BJH) method. The results show that the carbon coating process creates not only a layer of amorphous carbon on the surface of CoCO₃, but also a porous structure with pore size of ~30 nm. The amorphous carbon layer enhances the structural stability during the charging and discharging process, and the porous structure facilitates the movement of ions in the electrolyte, and thus improves its electrochemical performance. When the cycling performance was tested for 500 cycles, this CoCO₃/C material maintained a capacity of 539 mAh•g^-1 at 0.90C (1.00C = mAh•g^-1), showing its excellent cycling capacity. When the current rate was increased to 3.00C, the capacity was 130 mAh•g^-1. When the current rate was returned to 0.15C, its capacity was 770 mAh•g^-1, demonstrating the great rate performance and stability of CoCO₃/C.

Colloidal chalcopyrite CuInS₂ (CIS) quantum dots (QDs) were synthesized using copper(I) iodine (CuI) and indium(III) acetate (InAc3) as metal cationic precursors, and dodecanethiol (DDT) as the sulfur source and solvent. The microstructure and optical properties of the prepared CIS QDs were characterized by X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and UVVis absorption spectroscopy. The results showed that the CIS consisted of chalcopyrite phase and exhibited Cu-Au ordering. With prolonged reaction time, the grain sizes of the QDs became larger and the absorption edges of the CIS QDs showed a red-shift owing to the size-induced quantum confinement effect. For the first time, DDT-capped CIS QDs with narrow size distribution were connected to the inner surface of mesoporous TiO₂ films via a thioglycolic acid (TGA)-assisted adsorption approach, which was simple and easy to carry out. The adsorption behaviors of both TGA and the CIS QDs on the TiO₂ films were detected by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The results indicated that TGA was adsorbed onto the surface of TiO₂ via COOH groups while the ―SH group was exposed outside, and replaced DDT at the surface of the CIS QDs, leading to the attachment between TiO₂ and CIS. It was revealed that the CIS QDs of ~3.6 nm in size exhibited the best light absorption capacity and photovoltaic performance. An over-coating of CdS significantly improved the performance of the QDS

We report the synthesis of CdS polycrystalline thin films deposited with 0%, 0.88%, 1.78%, 2.58%, and 3.40% (volume fraction, φ) O₂ in sputtering Ar gas using a radio frequency magnetron sputtering method. The obtained CdS samples were characterized by X-ray diffraction, scanning electron microscope, Raman spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, and X-ray photoelectron spectroscopy. O incorporation led to the formation of compact and small CdS grains. The band gap values of the CdS thin films deposited with 0.88%and 1.78% O₂ were 2.60 and 2.65 eV, respectively, and were larger than that of CdS (2.48 eV) deposited without O₂ gas in sputtering Ar gas. In contrast, the band gap values of the CdS thin films deposited with 2.58% and 3.40% O₂ (2.50 and 2.49 eV, respectively) were consistent with that of CdS (2.48 eV) deposited without O₂ gas in sputtering Ar+O₂ gas. The CdS thin film deposited with 0.88% O₂ displayed the highest crystalline quality. Subsequently, CdTe thin films were deposited by radio frequency magnetron sputtering method on the surface of the CdS thin films. The CdTe thin films were characterized before and after high-temperature anneal treatment in a CdCl₂ atmosphere. The results showed that O incorporation into CdS led to the formation of considerably more closely packed and larger CdTe grains. The synthesis of CdS with large band gap values at room temperature is facile and effective using the current method. Therefore, the method presented herein is very promising for large-scale industrial production.

Owing to its high impedance, studying atmospheric corrosion using a traditional reference electrode (RE) is difficult. To obtain more accurate information on the electrochemical processes involved in atmospheric corrosion, it is necessary to improve the traditional RE. In this paper, the corrosion behavior of copper under an electrolyte droplet containing (NH₄)₂SO₄ was investigated by electrochemical impedance spectroscopy (EIS) and polarization measurements using a three-electrode system with a modified RE. The average corrosion rate increased with decreasing electrolyte volumes (from 1 to 20 μL) and with decreasing heights of the droplet at heights below 850 μm. The EIS and polarization results were in agreement, thereby demonstrating that the modified RE could be effectively used to study atmospheric corrosion under an electrolyte droplet.

Highly pure plastic crystal, 1-ethyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (P₁₂TFSI), was synthesized and purified by an easily industrializable recrystallization method. The P₁₂TFSI/LiFSI ionic liquid was obtained by mixing P₁₂TFSI with 30% (molar fraction, x) LiFSI. Electrochemical characterization methods including cyclic voltammetry, constant voltage polarization and charge/discharge at constant current were used to investigate the electrochemical window, stability vs Al corrosion, and battery performance of the ionic liquid.Awide electrochemical window of 5.00 V, non-corrosion of theAl current collector, and 0.92mS·cm^-1 of ionic conductivity at room temperature were observed. LiCoO₂/Li batteries assembled using this ionic liquid electrolyte showed good charge-discharge characteristics and cycle performance, comparable with those of carbonate-based electrolyte at low rate. The specific capacity of the LiCoO₂ remained 175 mAh·g^-1 after 20 cycles (95.1% capacity retention) despite cycling at a high voltage up to 4.50 V. These results indicate that the plastic crystal-based ionic liquid P₁₂TFSI/LiFSI could be potentially applied in high-energy density lithium secondary batteries.

The effects of sulfate concentration on the open circuit state and anodic polarization behavior of iron in dilute bicarbonate solutions were investigated using immersion tests, electrochemical measurements, and surface analysis techniques. In the absence of sulfate or in the presence of a low concentration of sulfate in dilute bicarbonate solutions, iron was in a passive state, with a corrosion potential of (-0.225±0.005) V. A high electrochemical impedance and low corrosion rate were obtained. No obvious active-passive transition was observed in the anodic polarization curves. In the presence of a high concentration of sulfate in dilute bicarbonate solutions, iron was in an active dissolution state, with a corrosion potential of (-0.790±0.010) V. A low electrochemical impedance, high corrosion rate, and typical active-passive transition in anodic polarization curves were observed and related to the sulfate concentration. In the presence of a high concentration of sulfate, the anodic polarization curves showed current peaks as a result of iron activation by sulfate ions. Sulfate ions of sufficiently high concentration in solutions degraded previously formed oxide layers on iron or transformed oxide layers in bicarbonate solutions. The transition of the open circuit state from passivity to active dissolution occurs at a lower sulfate concentration in a deaerated solution than in an aerated solution.

We synthesized Ni(OH)₂ nanowires/three-dimensional graphene composites using a hydrothermal method, and compared their properties with those of three-dimensional graphene, Ni(OH)₂ nanowires, reduced graphene oxide, and Ni(OH)₂ nanowires/reduced graphene oxide. The samples were characterized using Xray diffraction, scanning electron microscopy, thermogravimetric analysis, and N₂ physisorption measurements. The electrochemical performances were investigated using cyclic voltammetry and galvanostatic chargedischarge methods. The results showed that Ni(OH)₂ nanowires of width 20-30 nm were closely combined with graphene and crosslinked to one another to form a three-dimensional structure with a high specific surface area (136 m²·g^-1) and mesoporosity (pore diameter 20-50 nm). The mass fraction of Ni(OH)₂ nanowires in the Ni(OH)₂ nanowires/three-dimensional graphene composite was 88%. The maximum specific capacitance of the Ni(OH)₂ nanowires/three-dimensional graphene composite was 1664 F·g^-1 in 6 mol·L^-1 KOH electrolyte at 1 A·g^-1. The specific capacitance decreased by only 7% after 3000 cycles at 1 A·g^-1. A comparative study of the specific capacitances and cycling performances of Ni(OH)₂ nanowires, Ni(OH)₂ nanowires/reduced graphene oxide, three-dimensional graphene, reduced graphene oxide, and Ni(OH)₂ nanowires/three-dimensional graphene indicated that three-dimensional graphene with three-dimensional porosity and a larger specific surface area than conventional reduced graphene oxide enabled improved use of the active material and significantly enhanced the electrochemical performance of Ni(OH)₂ nanowires.

In the present work, we investigated the dynamics of charge collection and recombination in dyesensitized solar cells (DSSCs) spanning a large region of bias voltages using transient photoconductivity. The rate of charge collection was much faster than that of charge recombination at varied voltages, which was responsible for the nearly uniform charge collection efficiency. Based on this result, we simplified the diode characteristic model, which allowed us to directly fit the current-voltage (I-V) curve. A series of parameters related to the photo-to-electric processes in working DSSCs could be extracted from the proposed model, which could be used to evaluate the processes of charge generation, transport, and recombination in DSSCs, as well as the rectification of DSSC devices. We applied the fitting method to DSSCs with different 4-tert-butyl pyridine (TBP) concentrations of electrolyte. It was found that the rate of charge recombination significantly differed while that of charge collection was rather constant under different TBP concentrations, which was in good agreement with the results of I-V curve fitting. In addition, this research shows that the change of TBP concentration significantly affects the ideality factor (m) of DSSC devices.

A spherical Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode material for lithium-ion batteries was synthesized using a combination of modified carbonate co-precipitation and solid-state methods. The as-prepared material was analyzed using X- ray diffractometry (XRD), scanning electron microscopy (SEM), galvanostatic chargedischarge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results indicate that the material synthesized using this new method has a well-ordered layered structure, α-NaFeO₂ [space group: R3m(166)], a spherical morphology, and an average particle size of 157 nm. Electrochemical measurements showed that the material has a good rate capability and long-term cycling performance. At a current density of 0.1C (1.0C=180mA·g^-1) in the voltage range 2.7-4.3 V, the initial discharge capacity was 156.4 mAh·g^-1 and the coulombic efficiency was 81.9%. At 0.5C, 5C, and 20C, the specific capacities of the material were 136.9, 111.3, and 81.3 mAh·g^-1, respectively. After 100 cycles at 1C, the material retained 92.9% of its initial capacity; this is higher than those of materials prepared using conventional carbonate co-precipitation (87.0%).

Anatase TiO₂ shows excellent long-term cycling stability as an anode for sodium-ion batteries. However, the low specific capacity and poor rate capability resulting from its intrinsic low electrical conductivity limit its applications. In this work, TiO₂ nanoparticles were coated with reduced graphene oxide (RGO) using a combination of spray-drying and heat treatment. Electrochemical tests showed that the obtained RGO/TiO₂ composites had improved electrochemical performances. The reversible capacities of the RGO/TiO₂ [4.0% (w)] composites were 183.7 mAh·g^-1 (20 mA·g^-1), 153.7 mAh·g^-1 (100 mA·g^-1), and 114.4 mAh·g^-1 (600 mA·g^-1). Bare TiO₂ showed low capacities of 93.6mAh·g^-1 (20mA·g^-1), 69.6mAh·g^-1 (100mA·g^-1), and 26.5mAh·g^-1 (600 mA·g^-1). The 4.0%(w) TiO₂/RGO composites exhibited good cycling stability with a charge capacity of 146.7 mAh·g^-1 at a current density of 100 mA·g^-1 after 350 cycles, compared with 68.8 mAh·g^-1 for bare TiO₂. RGO modification is a promising method for improving the electrochemical performances of the sodium energystorage materials.

The electrochemical behavior and thermodynamic properties of GdCl₃ in LiCl-KCl molten salt system on both Mo and Al electrodes at 773 K were investigated. An open circuit chronopotentiogram was used to determine the equilibrium potentials and standard apparent potentials of the Gd(III)/Gd(0) system in the temperature range 723-873 K. The results showed that the equilibrium potentials and apparent standard potentials became positive with increasing temperature. The activity coefficients of GdCl₃ were calculated at different temperatures. The depolarization values were calculated by steady state polarization tests, and the theoretical extraction efficiency was obtained at 773 K. Potentiostatic electrolysis was performed to extract gadolinium from LiCl-KCl-GdCl₃ molten salt on Al electrodes at -1.5 V. The extraction efficiency was about 94.22% after 20 h. The Al₃Gd phase was identified in the deposit by X-ray diffraction (XRD).

A new Pt-based electrocatalyst with one-dimensional tubular Mn₃O₄-C as the catalyst support was synthesized by a dual-sacrificial template strategy. The morphology, structure, and composition of the Pt-Mn₃O₄- C composite were characterized by transmission electron microscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy, respectively. The electrochemical performance of Pt-Mn₃O₄-C was investigated by cyclic voltammetry. The results show that Pt nanoparticles with an average size of 1.8 nm are uniformly dispersed on tubular Mn₃O₄-C, and Pt-Mn₃O₄-C exhibits superior electrocatalytic activity and higher stability for methanol oxidation than the commercial E-TEK Pt/C catalyst (20% (w, mass fraction) Pt). The excellent performance of Pt-Mn₃O₄-C is attributed to the uniform dispersion of Pt nanoparticles on Mn₃O₄-C and the synergetic catalytic effect of Pt and Mn₃O₄.

In this work, N, S co-doped microporous carbon materials were successfully prepared using human hair and sucrose as carbon precursors via a two-step method that combined hydrothermal treatment and post-KOH activation. The morphology, pore texture, and surface chemical properties of the activated carbon materials were investigated by scanning electron microscopy, transmission electron microscopy, N₂ adsorption/desorption, X-ray photoelectron spectroscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. The electrochemical capacitive behavior of the prepared carbons was systematically studied in 6 mol·L^-1 KOH electrolyte. The maximum specific surface area of the prepared carbons was found to be 1849.4 m²·g^-1 with a porosity that mainly consisted of micropores. Nitrogen and sulfur contents varied from 1.6% to 2.5% and from 0.2% to 0.5% (atomic fraction (x)), respectively. The synergistic-positive effect of N, O, and S-containing groups caused the prepared carbons to exhibit a large pseudo-capacitance. High specific capacitances of up to 200 F·g^-1 at 0.2 A·g^-1 were observed, response to an energy density of 6.9 Wh·kg^-1. At a power density of 10000 W·kg^-1, the energy density was found to be 4.1 Wh·kg^-1. The present work highlights the significance of this new strategy to prepare N, S co-doped carbon materials from renewable biomass.

Carbonization of a nitrogen-containing polymer under inert atmosphere has been used to obtain nitrogen-enriched carbon materials. Herein, we synthesized dopamine-modified polypyrrole (PDA-PPy) via chemical polymerization, which was then carbonized under nitrogen atmosphere to produce nitrogen-doped porous carbon materials (NPC). The structure and morphology of the NPC were investigated by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). By regulating the molar ratio of pyrrole monomer to dopamine, the morphology of PDA-PPy and the capacitive performance of NPC could be controlled. At a current density of 0.5 A·g^-1, the specific capacitance of NPC-0.5 (the molar ratio of dopamine to pyrrole monomer is 0.5) is ca 210 F·g^-1. Even at a current density of 10 A·g^-1, the specific capacitance of NPC-0.5 is up to 134 F·g^-1 and the retention rate is 63.8%.

α-MnO₂ and Al-doped α-MnO₂ were synthesized via a hydrothermal method. The morphologies, structures, and electrochemical performances of as-synthesized un-doped and doped α-MnO₂ were studied. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) show that these un-doped and doped α-MnO₂ are nanotube shaped. The band gaps of α-MnO₂ are investigated by ultraviolet-visible absorption spectroscopy, which indicates that the band gap of α-MnO₂ decreases upon Al doping. The electrochemical performances of un-doped and doped α-MnO₂ as electrode materials for supercapacitors were measured by cyclic voltammetry (CV) and galvanostatical charge/discharge tests. The specific capacitances of un-doped and Al-doped α-MnO₂ respectively reach 204.8 and 228.8 F·g^-1under a current density of 50 mA·g^-1. It was discovered that the electrochemical impedance of Al-doped α-MnO₂ was decreased by Al doping analyzed using electrochemical impedance spectra (EIS), which provides a beneficial increase to its electrochemical specific capacitance. Enhanced specific capacitance and preferable cycling stability (up to 1000 cycles) for Al-doped α-MnO₂ mean that these systems are favorable prospects for application in supercapacitors.

LiVPO₄F/C, as a cathode material of lithium- ion batteries, was prepared by carbon thermal reduction assisted sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge cycles, cyclic voltammogram (CV), and electrochemical impedance spectroscopy (EIS) were employed to investigate the effects of sintering time and temperature on the structure and corresponding electrochemical performance of as prepared materials. At a sintering time of 4 h, pure phase LiVPO₄F/C material was obtained when the temperature is settled at 450 ℃. The as-produced LiVPO₄F/C exhibited discharge capacities of 193.2, 175.6, and 173.7 mAh·g^-1 at 0.1C, 0.5C, and 1.0C rates, respectively. Li₃V₂(PO₄)₃ impurities are formed and increased with increasing calcination temperature. When sintered at 650 ℃ Li₃V₂(PO₄)₃ is turn out to be the main phase. On the other hand, optimal duration time at high temperature could also inhibit the decomposition of LiVPO₄F and decrease the formation of Li₃V₂(PO₄)₃ impurities, improving electrochemical performance. Optimal conditions were found at a residence time of 3 h when the precursor is sintered at 550 ℃.

Multi-walled carbon nanotube (MWCNT)/TiO₂ composites were prepared using acid-treated MWCNT and titanium (IV) isopropoxide by a facile hydrothermal method. The morphology and structure of composites were characterized by field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis with differential scanning calorimetry (TGA-DSC), Raman and X-ray photoelectron spectroscopy (XPS). The results show that the cohesion effect of MWCNT/TiO₂ was due to the interaction between ―COOH group of acid-treated MWCNT and ―OH group of the anatase TiO₂ surface, which might form a similar chemical bonding (O＝C―O―Ti or C―O―Ti) interaction. The photoelectrochemical performance of dye-sensitized solar cell (DSSC) based on both MWCNT/TiO₂ counter electrode and thiolate/disulfide (T-/T₂) non-iodine redox couple was investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Tafel and voltage-photocurrent density curves. The results indicate that the reduction of T₂ to T^- at MWCNT/TiO₂ counter electrode was more effective than that of Pt counter electrode. Under optimized conditions (m(MWCNT)/m(TiO₂), mass ratio), DSSC achieved an optimal performance, such as open-circuit voltage of 0.63 V, short-circuit photocurrent density of 15.81 mA·cm^-2, fill factor of 0.65, and photon-to-electron conversion efficiency of 6.47%.

This article details a quick and simple method to prepare graphene oxide (GO) film and tune its energy level by adjusting the oxygen content. GO films with different layers were fabricated on fluorine-doped SnO₂ (FTO) conductive glass using the anodic electrophoretic deposition process. The degree of oxidation was regulated by cathodic electrochemical reduction. The as-prepared GO films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible absorption (UV-Vis) spectroscopy, X-ray photoelectron spectra (XPS), Raman spectroscopy and electrochemical analysis. The number of GO layers was varied between 77 and 570 by controlling the electrophoretic deposition time (from 20 to 350 s). Changing the degree of oxidation caused the optical gap of GO to vary between 1.0 and 2.7 eV, and also impacted the edge of the conduction band and the Fermi energy for the sample. As a p-type semiconductor, a p-n junction can be formed between reduced GO and FTO. Under simulated sunlight irradiance of 100 mW·cm^-2, the GO film with a deposition time of 300 s and reduction time of 120 s produced the highest photocurrent density of 5.25×10^-8 A·cm^-2.

Alloy 690 is one of the steam generator (SG) tubing materials in pressurized water reactors (PWR). The degradation of this alloy in alkaline solutions containing reduced sulfur is one of the main causes of stress corrosion cracking. In this study, the corrosion behavior of Alloy 690 in simulated alkaline crevice chemistry at 300 ℃ was investigated using polarization curves, scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Studying the effect of thiosulfate and sulfate on the properties of the passive film formed on Alloy 690 showed that the film formed at 300 ℃ was composed of an outer porous layer and an inner compact layer, and that the ion species presented in chloride solutions had a significant impact on the corrosion behavior of the alloy. The addition of thiosulfate increased the passive current density, decreased the transpassive potential, and therefore lowered the corrosion resistance. The presence of thiosulfate also led to a decrease in Cr levels and an increase in Ni levels in the passive layer. The thiosulfate can reduce sulfur at the film surface and enter into the film, causing an increased sulfide content in the film which decreases the corrosion resistance. However, experiments using sulfate had no obvious effect on film degradation as the ion had minimal interaction with the film.

Poly(1,4-bis(2- thienyl)-benzene) (PBTB) with a highly ordered porous nanostructure was successfully made using monolayer amine-modified polystyrene (PAS) as template in an electropolymerization method. The ordered porous polymer (OP-PBTB) film obtained can exhibit reversible color changes (yellow and purple) between the doping/dedoping states. Compared with the switching time of pure PBTB (colored time (t_c) and bleached time (t_b): 1.0 and 3.6 s at 1100 nm; 1.6 and 4.5 s at 620 nm), the switching time of OP-PBTB film is significantly shortened to 0.5 s (t_c) and 3.1 s (t_b) at 1100 nm, and 0.7 s (t_c) and 3.8 s (t_b) at 620 nm with the introduction of the porous nanostructure. In addition, the electrochemical impedance spectra (EIS) show that the ordered porous nanostructure offers OP-PBTB film a relatively low charge transfer resistance due to the larger surface area and shorter ion diffusion distance. This leads to higher intercalation/extraction capacities and faster ion diffusion speed, thus further shortening the switching time. Therefore, an effective way to improve the electrochromic performance of conducting polymers may be to construct ordered nanostructures using PAS as a template.

Gold nanoparticles (AuNPs) have a high extinction coefficient and a strong surface plasmon resonance, the latter of which is influenced by the size of AuNPs and the surrounding environment. In this article, a DNA electrochemiluminescence (ECL) sensor was fabricated based on the distance-dependence of semiconductor nanocrystals' ECL signal to AuNPs. AuNPs were first deposited on the surface of glassy carbon electrode (GCE) by cyclic voltammetry (CV). The mercaptopropionic acid-capped CdS quantum dots (QDs) used in this study can covalently bind with amino-terminated double-stranded DNA (dsDNA), via the ―CO―NH bond to obtain a QDs-dsDNA compound. The QDs-dsDNA compounds were assembled on the surface of AuNPs via an Au―S bond, using the other distal of dsDNA that is labeled with thiol, to create the CdS QDs-DNA/AuNPs/GCE ECL sensor. Experimental conditions, such as the QDs-dsDNA density on the surface of electrode and the deposition method of AuNPs, were then optimized. The surface properties of different modified electrodes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrochemical impedance spectroscopy (EIS). The effect of AuNPs on the ECL intensity of CdS QDs was investigated by controlling the DNA which lies between the AuNPs and the CdS QDs. The ECL signal was affected significantly by the length and type of DNA strands. The sensor was used to detect DNA damage from environmental pollutants and exhibited a highly sensitive response.

The catalyst layer in a proton-exchange-membrane fuel cell (PEMFC) was simulated based on a sphere-microstructure model that consisted of Pt/C particles and a mixed ionomer-pore phase. Pt/C particles were randomly distributed in the model and were treated as spheres with a normal distribution of their size assumed. Transport and electrochemical reactions in the model catalyst layer were calculated. The variation of oxygen level, overpotential, reaction rate, and cell current through the catalyst layer was discussed in relation to changes in electrode thickness and Pt/C particle size. The corresponding polarization curves were also analyzed. Through this analysis, optimal values for electrode thickness and particle size were achieved.

Polypyrrole coated carbon nanotubes (PPy/CNTs) were synthesized by the in-situ chemical polymerization of pyrroles on CNTs. Iron compounds were deposited on the PPy/CNTs to form an Fe-PPy-CNTs composite using ferrous ammonium sulfate as the iron precursor by liquid phase precipitation. Catalysts wherein iron-based compounds were loaded onto nitrogen doped CNTs (FeNCNTs) were prepared by heat treatment of the composites. X-ray diffraction (XRD) analysis shows that the heat treatment of Fe-PPy-CNTs caused the Fe₃O₄ in the composite to convert to Fe₃N and Fe. The FeNCNT700 prepared at 700 ℃ contains Fe₃O₄ and Fe. We conclusively show that in both FeNCNT800 and FeNCNT900 that were prepared at 800 and 900 ℃, respectively, Fe₃N and Fe formed. With an increase in temperature the total amount of nitrogen in the FeNCNTs decreases and the nitrogen containing functional groups convert from pyrrolyic-N to pyridinic-N and graphitic- N. Electrochemical analyses show that the FeNCNT800 and FeNCNT900 that contain Fe₃N exhibits good activity toward the oxygen reduction reaction (ORR). Compared with FeNCNT900, FeNCNT800 has better ORR activity and stability because of its larger specific surface area, higher nitrogen content and higher ratio of graphitic-N in the nitrogen containing functional groups. This enhances the oxygen adsorption ability of the catalyst and weakens the O―O bond.

Uniform nickel oxide nanoparticles (~10 nm) embedded in porous hard carbon (HC) spheres (90- 130 nm) for high performance lithium ion battery anode materials were synthesized via a hydrothermal method followed by impregnation and calcination. The HC spheres, which had abundant micropores and plentiful surface functional groups, allowed firm embedding and uniform dispersion of the NiO nanoparticles. The as-prepared HC/NiO composite anode exhibited excellent electrochemical performance, including high reversible capacity (764 mAh·g^-1), good cycling stability (a high specific capacity of 777 mAh·g^-1 after the 100th cycle at a current density of 100 mA·g^-1, a capacity retention rate of 101%), and high rate capability (380 mAh·g^-1 even at 800 mA·g^-1). These excellent electrochemical properties were attributed to the unique structure of NiO nanoparticles tightly embedded in a hard carbon matrix. Anode materials with such a structure have the advantages of improved electronic conductivity, more accessible active sites for lithium ion insertion, and short diffusion paths for lithium ions and electrons. The observed“synergistic effects”between the hard carbon and NiO represent an advance in the electrochemical performance of such composites. The present method is an attractive route for preparing other hard carbon/metal oxide composite anodes for lithium ion batteries.

Li₃V₂(PO₄)₃/C cathode material was synthesized by the sol-gel method. The electrochemical properties of the sample in different voltage ranges (3.0-4.5 V and 3.0-4.8 V) were investigated by galvanostatic charge/discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Results show that the cycling performance and rate capability of Li₃V₂(PO₄)₃/C in voltage range of 3.0-4.8 V are worse than those in voltage range of 3.0-4.5 V. The initial specific discharge capacity in voltage range of 3.0-4.5 V at 0.1C rate (1C=150 mA·g^-1) is 127.0 mAh·g^-1, and 99.5% of the initial capacity was maintained after 50 cycles in contrast to 168.2 mAh·g^-1 and 78.5% in voltage range of 3.0-4.8 V. The discharge capacities in voltage ranges of 3.0-4.5 V and 3.0-4.8 V are 99.0% and 80.7% of the initial 0.1C rate respectively when the charge/discharge rate recovered to 0.1C rate after the high rate test. Part of the third lithium ion may be extracted at less than 4.5 V after several cycles in voltage range of 3.0-4.8 V with a capacity increase of 7.4%. CV results indicate that the irreversible capacity fading between 3.0 and 4.8 V may be attributed to irreversible behavior of the first lithium ion. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results show that the structure of Li₃V₂(PO₄)₃ changes slightly after operating between 3.0 and 4.8 V. Inductively coupled plasma (ICP) results indicate the presence of dissolved V in the cycled electrolytes. The structural distortion and the V dissolved in the electrolyte may be the main reasons for the decrease in capacity.

Hybrid organic-inorganic lead halide perovskite solar cells (PSCs) have recently undergone rapid progress and exhibit high photoelectric conversion efficiencies of up to 19.3%. As light-absorber in PSCs, the hybrid organic-inorganic lead halide perovskite cannot be used in large-scale applications because of its high Pb content. In this work, we replaced some Pb with Sr to synthesize a novel perovskite CH₃NH₃Sr_xPb_(1-x)I₃ and used it as a light-absorber in PSCs. Compared with CH₃NH₃PbI₃, CH₃NH₃Sr_0.3Pb_0.7I₃ is a better light-absorber but the corresponding photovoltaic performance in PSCs decreased obviously.

A zirconium nanocrystalline coating has been fabricated on a Ti-6A1-4V alloy bipolar plates using a double cathode glow discharge technique to improve the corrosion resistance and reduce the interfacial contact resistance in polymer electrolyte membrane fuel cells (PEMFCs). The microstructure of Zr coating was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The microstructure of the Zr coating was found to be continuous and compact; consisting of deposited and diffusion layers. The deposited layer was 30 μm thick and composed of equiaxed grains with an average grain size of around 15 nm, whereas the diffusion layer was 10 μm thick with a gradient distribution of alloying elements, which offered a smooth transition of mechanical properties that were suitable for improving the adhesion strength of the Zr coating on the Ti-6A1-4V substrate. The electrochemical behavior of the Zr coating was evaluated in 0.5 mol·L^-1 H₂SO₄ solution containing 2 mg·L^-1 of HF solution at 70 ℃ to simulate the environment found in a PEMFC. The solution was purged with H2 (simulated PEMFC anodic environment) or air (simulated PEMFC cathodic environment). The Ecorr of the deposited Zr nanocrystalline coating was much higher than that of the Ti-6A1-4V alloy in the simulated PEMFC environment. At the applied cathode (+0.6 V) potentials for PEMFCs, both the Zr nanocrystalline coating and Ti-6A1-4V alloy were in the passive region, but the passive current density of the as-deposited Zr nanocrystalline coating was four orders of magnitude lower than that of the Ti-6A1-4V alloy. At the applied anode (-0.1 V), the Zr nanocrystalline coating exhibited characteristic cathodic protection behavior. The results of electrochemical impedance spectroscopy (EIS) showed that the values of the capacitance semicircle, phase angle maximum and frequency range were larger than those of the Ti-6A1-4V alloy in the simulated PEMFC environment when the phase angle was near -80°. Moreover, the Zr nanocrystalline coating effectively improved the conductivity and hydrophobicity of the Ti-6A1- 4V alloy bipolar plate.

A Pt/TiO₂ nanofiber catalyst has been prepared through the combination of an electrospinning technique with a reductive impregnation method. The compositions, morphologies and structures of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS). The results showed that the crystal phase of the TiO₂ nanofibers was composed of anatase and rutile TiO₂. Pt nanoparticles were found to be uniformly distributed on the surface of the TiO₂ nanofibers with an average size of 4.0 nm. The mass fraction of Pt in the Pt/TiO₂ nanofiber catalyst was about 20%. The electrocatalytic activities of the samples towards the oxidation of methanol were measured by cyclic voltammetry and chronoamperometry using a three-electrode system in an acidic solution. Compared with Pt/P25 and commercial Pt/C catalysts containing the same quality percentage of Pt nanoparticles, the Pt/TiO₂ nanofiber catalyst exhibited higher catalytic activity towards the oxidation of methanol and better stability.

The electrochemical behavior of Dy(Ⅲ) in LiCl-KCl melts and the alloying mechanism of Dy-Ni alloys were investigated by cyclic voltammetry, square wave voltammetry, and open circuit chronopotentiometry. Cyclic voltammetry and square wave voltammetry experiments indicated that the reduction of Dy(Ⅲ) ions to Dy metal occurred in a single step with the exchange of three electrons. Compared with cyclic voltammograms on an inert W electrode, three reduction peaks are observed. This indicates the under-potential deposition of Dy(Ⅲ) on a reactive Ni electrode because of the formation of Dy-Ni alloy compounds. Dy-Ni alloys were prepared by potentiostatic electrolysis at -1.6, -1.8, and -2.0 V and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). The results confirm that different Dy- Ni compounds: DyNi₅, Dy₂Ni₇, and DyNi₂ can be selectively obtained by potentiostatic electrolysis at different potentials.

A La₂CoNiO₆ inorganic nanofiber supercapacitor electrode material was successfully prepared from a polyvinylpyrrolidone/lanthanum nitrate-cobalt acetate-nickel acetate (PVP/LCN) precursor by electrostatic spinning. Its surface morphology and structure were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). We found that the fibers were connected through rhombohedral La₂CoNiO₆ nanoparticles resulting in a linear spatial network structure. The electrochemical performance of the as-prepared inorganic nanofibers was characterized by cyclic voltammetry (CV), chronopotentiograms (CP), and cycle life tests. The results show that the La₂CoNiO₆ nanofiber electrode material has good capacitor performance. For the three-electrode system the electrode achieved a respectable specific capacitance of 335.0 F·g^-1 at 0.25 A·g^-1. For the symmetrical two-electrode system the electrode achieved a specific capacitance of 129.1 F·g^-1 at the same current density.

Three-dimensional reduced graphene oxide (RGO)/polyaniline (PANI) composite has been prepared in a single step by the ultrasonic irradiation of a suspension of graphite oxide gels and PANI nanowire using a hydrothermal method. Scanning electronic microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectra (XPS), and electrochemical measurements were performed to investigate the morphology, structure, and supercapacitive performance of the composite. The result showed that the composite maintained the basic morphology of RGO, and that the PANI was inlayed inside the RGO network. An outstanding supercapacitive performance was obtained when the mass ratio of graphite oxide and PANI was 1:1. Furthermore, the capacities reached 758 and 400 F·g^-1 at 0.5 and 30A·g^-1, respectively. The retention rate was found to be 86% after 1000 cycles at 1 A·g^-1. These results therefore indicate that this new composite possesses good rate capability and cycle stability, and that its supercapacitive performance is better than that of pure RGO or PANI. The excellent supercapacitive performance of this composite can be attributed to the mutual synergy of RGO and PANI.

Anickel-based composite filmwas fabricated on Ni foil, by two-electrode anodization and galvanostatic charge-discharge (GCD) treatment. The surface morphology, states of chemical species, and crystal structure of the filmwere characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The electrochemical performance was tested using an electrochemical workstation and battery program-control test system. The test results indicated that the filmpossessed a nanoflower-like morphology, and consisted of NiO, α-Ni(OH)₂ and β-Ni(OH)₂. The NiO-α-Ni(OH)₂-β-Ni(OH)₂ compounds exhibiting a high specific capacitance, superior rate capability, and good cyclability (1509 F·g^-1 at 6.7A·g^-1, 1120 F·g^-1 at 66.7 A·g^-1, after 2000 cycles, the capacitance of the filmremained unchanged).

The single-molecule junction conductance of terephthalic acid binding to Cu andAg electrodes was measured by an electrochemical jump-to-contact scanning tunneling microscopy break junction (ECSTM-BJ) approach. The Cu andAg electrodes were formed in-situ, via electrodeposition froma solution. The conductance histograms of the single-molecule junctions formed via the binding of terephthalic acid to the Cu and Ag electrodes showed a well-defined shape, in the absence of any data selection. The single-molecule junction conductance values for the terephthalic acid binding to the Cu electrode were 11.5 nS (high conductance) and 4 nS (lowconductance), while the high and lowconductance values for theAg electrode were 10.3 and 3.8 nS, respectively. The high conductance values were typically approximately three times larger than the low conductance values, for both the Cu and the Ag electrodes. The conductance (G) value for the terephthalic acid followed the order of G_Cu>G_Ag, which indicated the different electronic coupling efficiencies between the molecule and electrodes. In contrast with the single set conductance value measured for alkanedicarboxylic acid using the same approach, two set conductance values were found for the terephthalic acid junctions with the Cu and Ag electrodes. These results illustrated the important role of the backbone of the chain in conductance measurements. The present work demonstrated the influence of the electrode and the molecular structure on the single-molecule junction conductance.

The effects of different cathode current collectors (stainless steel, nickel, copper, and titanium) on the electrochemical performance of rechargeable magnesiumbatteries were investigated. Chevrel phase Mo₆S₈ acted as the cathode, (PhMgCl)₂- AlCl₃/tetrahydrofuran (THF) (the second generation electrolyte) as the electrolyte, and magnesium as the anode. Constant current discharge-charge results indicated that the electrochemical polarization of the electrode on stainless steel was the smallest and its cycling stability was the best, followed by nickel, copper, and titanium. Microstructure analyses for the electrodes and current collectors before and after discharge-charge were analyzed to investigate the differing electrochemical performance. The electrolyte corroded the current collectors to differing degrees. The surfaces of the electrodes differed after coating the active material on different current collectors. The corrosion potentials of the current collectors decreased after loading the active material. This resulted in the current collectors being more susceptible to corrosion by the electrolyte.

Dye-sensitized solar cells (DSCs) have aroused much interest because of their low cost and comparatively high power conversion efficiency. Stability is paramount for any photovoltaic technology. Traditional liquid electrolytes tend to leak and evaporate, which limits the long-termperformance of the DSC. N,N'-1,5-Pentanediylbis-dodecanamide was synthesized and used as a low molecular mass organogelator (LMOG), to gelate an ionic liquid electrolyte (ILE) and fabricate a quasi-solid-state DSC(QS-DSC). Differential scanning calorimetry indicated that the gel-to-solution transition temperature of the ionic gel electrolyte (IGE) was 104.7℃, which indicated good intrinsic stability. Electron transport and recombination were investigated by cyclic voltammetric (CV) and electrochemical impedance measurements, and intensity-modulated photocurrent and photovoltage spectroscopy (IMPS and IMVS) measurements. Electron recombination at the TiO₂ photoanode/ electrolyte interface was accelerated by the cross-linked gel network. The shorter electron recombination lifetime decreased the photoelectric conversion efficiency of the QS-DSC, compared with the ILE-based DSC. The photoelectric conversion efficiency of the QS-DSC exhibited no change during accelerated aging test for 1000 h, while that of the ILE-based DSC decreased to 86% of its initial value.

Electrochemical exfoliation of graphite rods under the action of an electric field force led to the formation of two-dimensional (2D) graphite nanosheet arrays (GNSAs) perpendicular to the surface of the graphite substrate and parallel to each other in arrangement. Subsequently, SnO₂/graphite nanosheet array (SnO₂/GNSA) composite electrodes were prepared by the cathodic reduction electrodeposition method. The morphology, composition, and microstructure of the samples were characterized using field emission scanning electron microscopy (FESEM), powder X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy, respectively. Electrochemical measurements showed that the composite electrodes achieved specific capacitance values as high as 4105 F·m^-2 in the potential window up to 1.4 V with a scan rate of 5 mV·s^-1 in 0.5 mol·L^-1 LiNO₃ solution. Asymmetric supercapacitor fabricated with the as-prepared SnO₂/GNSAs exhibited excellent capacitive performance with energy density of 0.41 Wh·m^-2 in the potential window up to 1.8 V and retention of 81% after 5000 cycles.

Aminated graphene (GP-NH₂) was fabricated via the modification of graphite oxide (GO) with 3-aminopropyltriethoxysilane (AMPTS), and the covalent grafting of the amine functional groups was confirmed using Fourier transform infrared (FTIR) spectroscopy and energy-dispersive X-ray (EDX) spectroscopy. The aminated graphene (GP-NH₂)/activated carbon (AC) composite electrode (GP-NH₂/AC) was prepared, using the GP-NH₂ as an additive. An AC||GP-NH₂/AC asymmetric capacitor for capacitor deionization was then assembled using the GP-NH₂/AC electrode as the positive electrode and AC as the negative electrode. A salt removal of 7.63 mg·g^-1 was achieved using the AC||GP-NH₂/AC capacitor, and current efficiency was increased to 77.6%. AGP-SO₃H/AC electrode was then prepared by mixing AC with sulfonated GP. With GP-NH₂/AC as the positive electrode, and GP-SO₃H/AC as the negative electrode, a GP-SO₃H/AC||GP-NH₂/AC asymmetric capacitor was assembled for capacitive deionization. An average desalting rate of 0.99 mg·g^-1·min^-1 was achieved, almost five times higher than that achieved using an AC||AC symmetric capacitor. The chargedischarge rate showed a 30% increase. The existence of the intrinsic charge on the electrode surface greatly inhibited the migration of counter ions, so that the current efficiency was significantly enhanced (to 92.8%) in comparison with the value achieved using an AC||AC capacitor (40%). These results demonstrated that the functionalized graphene in the AC electrode not only enhanced the conductivity, but also controlled the selective adsorption of ions, thereby significantly improving the deionization performance.

Specific ion effects have been observed in a wide range of phenomena at solid-liquid interfaces. Recent studies have indicated that the origin of these effects in some relatively low-electrolyte-concentration systems is the ion polarization in the strong electric field near the interface, rather than dispersion forces, classical induction forces, ionic size, or hydration effects. These effects cause the counterions near the interface to become strongly polarized (with a polarization that is nearly ten thousands times stronger than classical polarization). This strong polarization causes that the Coulomb force exerted by the polarized ions near the interface is far greater than the force generated by the ionic charge, which is reflected in the fact that the effective charge number of polarized ions is much larger than their original charge number. We therefore used the effective charge number of strongly polarized cations to quantitatively characterize the strength of specific ion effects in colloid systems. In this study, we observed the strong, specific ion effects of Na⁺, K⁺, Ca²⁺, and Cu²⁺ in the montmorillonite-humic acid composite aggregation process. Furthermore, we established a method to calculate the effective charge number of polarized cations based on the critical coagulation concentration (CCC) measured using dynamic light scattering. We successfully obtained the effective charge number of polarized ions. The experimental effective charge numbers for Na⁺, K⁺, Ca²⁺, and Cu²⁺ were Z_{Na(effective)}=1.46, Z_K(effective)=1.86, Z_{Ca(effective)}=3.92, Z_{Cu(effective)}=6.48, respectively. These results showed that the non-classical polarization greatly enhanced the effective charge number of ions, greatly enhancing the Coulomb force exerted by the ions; and that the more electronic layers the ions had and the stronger the ionic polarization, the more the effective charge of ions increased.

An Mg(Ⅱ) and Ti(Ⅳ), iso-molar, co-doped cathode material LiMn_1.9Mg_0.05Ti_0.05O₄ for lithium-ion batteries was successfully synthesized via a sol-gel method, using lithium hydroxide, manganese acetate, magnesium nitrate, and butyl titanate as raw materials, and citric acid as a chelating agent. The as-prepared materials were characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical tests (including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements). The results demonstrated that the cathode material LiMn_1.9Mg_0.05Ti_0.05O₄, which was obtained after calcination at 780℃ for 12 h, exhibited a fine microstructure and good electrochemical performance. When cycled at 4.35-3.30 V at room temperature, LiMn_1.9Mg_0.05Ti_0.05O₄ delivered a discharge specific capacity of 126.8 mAh·g^-1 at 0.5C rate, and maintained a capacity of 118.5 mAh·g^-1 after 50 cycles; the capacity retention of this material reached 93.5%. This material showed a discharge-specific capacity of 111.9 mAh·g^-1 at 0.5C rate after 30 cycles, when it was cycled at 55℃; under these conditions the capacity retention reached 91.9%, far superior to the capacity retention of undoped LiMn₂O₄. The iso-molar co-doping of LiMn₂O₄ with Mg(Ⅱ) and Ti(Ⅳ) ions led to significant modification of the electronic and ionic conductivity, and increased the rate properties and electrochemical performance of the spinel lithium manganate at elevated temperatures.

Electrochemical impedance spectroscopy (EIS) is a very useful technique for studying electrochemical behavior. The ideal Nyquist plot of electrochemical impedance spectroscopy for an electrical double-layer capacitor (EDLC) consists of a 45° line in the high-middle frequency region and a vertical line in the low frequency region, which can be explained by the transmission line model with pore size distribution. However, a semicircle loop in the high frequency region has been found in many studies. Hence, in this study, an equivalent model is proposed, in which the semicircle loop is ascribed to the contact resistance and contact capacitance between particles of activate materials, and between the activated carbon (AC) electrode and current collector. The effects of the charging process, conductivities of the active material and electrolyte, content of conductive additive and binder, porous separator, mass loading, and exerted pressure to the electrode on the EIS spectra of EDLCs were experimentally investigated. Among these effects, the most significant factors were the charging cut-off voltage, conductivity of activated carbon, content of conductive additive, and exerted pressure.

Three-dimensional reduction of graphene oxide with a series of different degrees of reduction was performed by the hydrothermal method in the temperature range from 120 to 220 ℃, with graphene oxide sols as the precursor and prepared by graphite oxide gels. The effect of the temperature of the hydrothermal reaction on the materials appearance, structure, and super capacitor performance was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. The results show that the prepared three dimensional reduction of graphene oxide was porous and reticulated, and its volume and inner mesh aperture gradually decreased with increasing temperature, while its degree of reduction and order increased at the same time, and its structure gradually transformed to the graphite oxide structure. However, thematerials' specific capacitance and energy density showed the tendency of first increasing and then decreasing, with the electric double-layer capacitor mainly remaining. The three-dimensional reduction of graphene oxide materials at 180 ℃ resulted in the best super capacitor performance, with a specific capacitance of 315 F·g^-1 when the current density was 0.5 A·g^-1 and 212 F·g^-1 when the current density was 10 A·g^-1. Its energy density was 40.5 Wh·kg^-1 and its specific capacitance was 86% after 5000 cycles, with all these properties indicating its good super capacitor performance.

To improve the sensitivity of molecular imprinted electrochemical sensors, a molecularly imprinted polymer (MIP) film for the determination of phenobarbital (PB) was electropolymerized on a CuO nanoparticlemodified glassy carbon electrode. Methacrylic acid was used as the functional monomer and ethylene glycol maleic rosinate acrylate as a cross-linking agent in the presence of supporting electrolyte (tetrabutylammonium perchlorate). The electrochemical properties of CuO nanoparticle-modified molecularly imprinted and non-imprinted polymer (NIP) sensors were investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The results showed that the electrochemical properties of the CuO nanoparticle-modified MIP sensor were completely different from those of NIP sensors. X-ray diffraction confirmed that the nanoparticles were CuO. The morphology of the CuO nanoparticle-modified MIP sensor was examined under a scanning electron microscope. The CuO nanoparticles were uniformly distributed on the surface of the modified glassy carbon electrode, which improved the recognition sites of the modified MIP sensor. The response value of the DPV peak current showed linear dependence on the PB concentration in the range 1.0×10^-8 to 1.8×10^-4 mol·L^-1 (linear regression coefficient =0.9994) with a detection limit (S/N=3) of 2.3×10^-9 mol·L^-1. The results indicated that the CuO nanoparticle-modified MIP sensor is one of the most sensitive and selective sensors for PB determination. The prepared sensor was successfully applied for the determination of PB in practical samples and the recovery ranged from 95.0% to 102.5%.

Zn-Al-[V₁₀O₂₈]^6- layered double hydroxide (LDH-V) as a type of corrosion inhibitor was prepared with the co-precipitation method using one solution containing zinc and aluminum nitrates precursors and a second solution containing Na₃VO₄, where the decavanadate anion is speciated at pH 4.5. The hybrid solgel solution was prepared from 3-glycydoxypropyltrimethoxysilane (GPTMS) as the organic precursor sol and zirconium n-propoxide (TPOZ) as the inorganic precursor sol. The doped coatings were obtained by dip coating the way that the samples were immersed into solutions with different LDH-V concentrations (0.0, 0.25×10^-3, 0.75×10^-3, 1.5×10^-3, 3.0×10^-3 mol·L^-1). The morphology and corrosion resistance of the solgel coating doped with different LDH-V concentrations were studied. The sol-gel coatings were investigated by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The salt spray test was used to evaluate the corrosion resistance of the different coatings. The corrosion behavior of the coatings was evaluated by electrochemical impedance spectroscopy (EIS) during immersion in 0.05 mol·L^-1 NaCl solution. The results showed that LDH-V not only improves the corrosion resistance of the coating, but also provides a function for self-healing of broken coatings. However, when the LDH-V doping concentration was high, it destroyed the integrity of the coatings and decreased the corrosion resistance of the coatings. The best LDH-V doping concentration was 1.5×10^-3 mol·L^-1.

Li₂MnO₃ materials were synthesized by solid state reactions. A series of Li₂MnO₃ thin films were fabricated at different temperatures under O₂ by pulsed laser deposition (PLD) using a home-made Li₂MnO₃ target. The structure and morphology of the as- prepared Li₂MnO₃ thin films were characterized by X- ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). Their electrochemical performance was also investigated. The results show that the crystallinity of the thin films increased with an increase in deposition temperature, and the thin film electrode prepared at lower than 25 ℃ did not work well. The highest electrochemical activity was achieved by the thin film deposited at 400 ℃, and this result is consistent with our previous report on powder materials. The Li₂MnO₃ thin film electrodes deposited at 400 and 600 ℃ exhibited lower discharge voltage decay upon cycling compared with the powder electrode.

Size-dependent electron injection processes in CuInS₂ (CIS) quantum dot sensitized solar cells (QDSSCs) were studied. CuInS₂ quantum dots (QDs) with various diameters were synthesized and sensitized on TiO₂ films. The energy levels of the CuInS₂ QDs were measured by cyclic voltammetry. The rates and efficiencies of electron transfer from CuInS₂ QDs to TiO₂ films were determined by time-resolved photoluminescence spectroscopy. It was found that the rate of electron injection increased with a decrease in QD size while the efficiency of electron injection decreased. Furthermore, the power conversion efficiency, the short-circuit photocurrent, and the fill factor (FF) of the QDSSCs increased with an increase in QD size. The enhanced performance of the QDSSCs was attributed to the increase in electron injection efficiency. These results indicate that the performance of the QDSSCs could be optimized by varying the size of the QDs.

Based on the cyclic voltammogram (CV) of TiO₂/Ti electrodes in Cu²⁺ ion solution, we fabricated Cu₂O and Cu particles onto TiO₂ flat surfaces separately or simultaneously by adjusting the applied potentials during electrodeposition. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that Cu₂O and Cu have different growth modes: Cu₂O particles crystallize on the TiO₂ surface separately while Cu particles nucleate on previously grown particles, forming a stacked particle structure. This growth behavior can be explained by the different electron transfer behavior on the Cu₂O/TiO₂ and Cu/TiO₂ interfaces and this is determined by their bandgap alignments. Compared with a pure TiO₂ photoanode, a significant enhancement of the photocurrent was observed for both the Cu₂O/TiO₂ and Cu/TiO₂ heterostructures. A potential region exists where Cu₂O and Cu grow on the TiO₂ surface simultaneously and the corresponding photocurrent is relatively stable and reaches a maximum. UV-Vis diffuse reflectance spectroscopy, electrochemical impedance spectroscopy (EIS), and photocurrent vs potential characteristics revealed that the visible light absorption by Cu₂O and Cu contributes significantly to the photocurrent. Cu/TiO₂ resulted in greater broadband visible light utilization during the photoelectric conversion. Additionally, the increased zero-current potential and the effective charge separation as well as the rapid carrier transfer on the electrode/electrolyte interface are also related to the enhanced photoelectrochemical properties.

Amanganese dioxide (MnO₂)-graphene composite material with a unique structure consisting of MnO₂ surrounded by graphene sheets was prepared by a simple hydrothermal and thermal decomposition method. The morphology and structure of the obtained materials were examined by scanning electron microscopy, transition electron microscopy, Raman spectroscopy, X-ray diffraction, and N₂ adsorption-desorption. Electrochemical properties were evaluated by cyclic voltammetry, galvanostatic charge- discharge and electrochemical impedance spectroscopy. The specific surface area increased from 109 to 168 m²·g^-1 for the composite containing 15% (w) graphene. The specific capacitance also increased from 294 to 454 F·g^-1 at a current density of 0.2 A·g^-1 in an aqueous electrolyte supercapacitor. Moreover, after 2000 cycles of a galvanostatic charge-discharge test, the hybrid electrode still had excellent cycle stability (92% retention rate).

A bamboo leaf inhibitor (designated PSLE) was extracted from Phyllostachys sulphurea (Corr. Riviere) leaves using a series of C₂H₅OH-water solutions (20%-80% (volume fraction)). The solutions were characterized by Fourier transform infrared (FTIR) spectroscopy and ultraviolet- visible (UV-Vis) spectrophotometry. The total flavonoid content of the PSLE was determined. The inhibition effect of PSLE toward the corrosion of aluminum in HCl solution was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Density functional theory (DFT) quantum chemical calculations including solvent effects were used to investigate the adsorption of light by the two major components vientin and isovientin. The results show that PSLE is a good inhibitor and the adsorption of PSLE on the aluminum surface obeys the Langmuir adsorption isotherm. The inhibition efficiency increases with PSLE concentration while it decreases with temperature and HCl concentration. A good correlation exists between the total flavonoid content and the inhibition performance. This implies that the flavonoids are the major contributor to inhibition activity. PSLE behaves as a cathodic inhibitor. The EIS spectra are characterized by one large capacitive loop at high frequencies followed by a large inductive loop at low frequency values. The impedance value increases with increasing inhibitor concentration. SEM results confirm that the corrosion of aluminum is retarded remarkably by PSLE. The quantum calculation results indicate that the adsorption center of either vientin or isovientin is mainly a flavonoid backbone structure (FBS).

Pyrazolyl magnesium halide/tetrahydrofuran (THF) solutions were obtained by the simple reaction of pyrazole compounds with Grignard reagents in THF. Their electrochemical performances as rechargeable magnesium battery electrolytes are reported. The pyrazolyl magnesium halide/THF solutions were characterized in term of anodic stability and reversibility of magnesium deposition-dissolution using cyclic voltammetry and galvanostatic charge-discharge techniques. The composition and morphology of the deposit were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is concluded that the substituents on the pyrazole compound and the molar ratio of the pyrazole to the Grignard both affect the electrochemical performance. An electrolyte consisting of 1 mol·L^-1 1-methylpyrazole-PhMgCl (1:1 molar ratio)/THF has an anodic oxidation decomposition potential of 2.4 V (vs Mg/Mg²⁺) on stainless steel (SS), a low potential for magnesium deposition-dissolution, and a high cycling reversibility, and can be prepared easily, making it a promising candidate for rechargeable battery electrolytes.

To improve the cycling performance of lithium-rich cathode materials, Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ and Li_1.2Mn_0.54-xNi_0.13Co_0.13Zr_xO₂ (x=0.00, 0.01, 0.02, 0.03, and 0.06) were synthesized by a combustion method. The structure and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical performances were examined by cyclic voltammetry (CV), electrochemical AC impedance spectroscopy, and galvanostatic charge-discharge cycling. The results indicate that all of the doped samples have a layer of α-NaFeO₂. When charged and discharged at 0.1C and 1.0C (1.0C=180 mA·g^-1) in the voltage range of 2.0-4.8 V, the initial discharge capacities of Li_1.2Mn_0.52Ni_0.13Co_0.13Zr_0.02O₂ were 280.3 and 206.4 mAh·g^-1, respectively. Moreover, the capacity retention after 50 cycles improved from 73.2% to 88.9% at 1.0C at room temperature. Meanwhile, this system delivered a higher discharge capacity of 76.5 mAh·g^-1 than that of the bare materials (15 mAh·g^-1) at 5.0C after 50 cycles. Electrochemical performances of the doped samples were improved at a 2.0C rate at different temperatures (50, 25, and -10 ℃). Furthermore, compared with the undoped material, the specific discharge capacity increased by 61.1% at -10 ℃ after 50 cycles.

Fe₃O₄/graphene composites with a conductive, porous three-dimensional (3D) graphene network were synthesized through a facile method. In the preparation process, Fe(OH)₃ colloid was formed in situ by adding FeCl₃ solution to a boiling graphene oxide (GO) suspension, with Fe(OH)₃/GO precipitated because of the electrostatic interaction between the two components. The precipitate was separated and added to a second GO suspension to achieve additional GO encapsulation. This self-assembled Fe(OH)₃/GO precursor was then hydrothermally and heat treated, resulting in the formation of Fe₃O₄/graphene composites. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy results revealed that the Fe₃O₄/graphene composites possess a favorable 3D porous graphene network embedding 50- to 100-nm-sized Fe₃O₄ nanoparticles. The Fe₃O₄/graphene composites exhibit good electrochemical performance as an anode material for Li-ion batteries. The electrode composed of the Fe₃O₄/graphene composite delivered a capacity of 1390 mAh·g^-1 for the first lithiation and retained a capacity of 819 mAh·g^-1 after 50 cycles. The electrodes also exhibited good rate capability. The present results demonstrate that the electrochemical performance of the Fe₃O₄/graphene composite is highly sensitive to its preparation procedure and to the resulting nanostructure. Each of the four preparation procedures was experimentally shown to be important for achieving the final nanostructure and good electrochemical performance. A formation mechanism for the Fe₃O₄/graphene composite is also proposed.

Octadecylamine functionalized graphene (ODA-G) was synthesized by the grafting of graphene oxide (GO) with ODA followed by reduction with hydrazine hydrate. Subsequently, ODA-G/polyaniline (PANI) composites were prepared using a facile solvent-blending procedure. ODA-G and ODA-G/PANI composites were characterized by Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy, and transmission electron microscopy (TEM). The electrochemical properties of the composites were measured based on cyclic voltammetry (CV), galvanostatic charge/discharge, and ac impedance spectroscopy. The results show that ODA-G as a support material provides additional electron transfer paths, as well as active sites, for the electrochemical redox reaction of PANI, which helps to increase its pseudocapacitance. A specific capacitance of 782 F·g^-1 is obtained for 2%(w)ODA-G/PANI at a current density of 1.0 A·g^-1, compared with 426 F·g^-1 for PANI. Furthermore, ODA-G/PANI exhibits better stability than PANI.

A lithium-rich solid-solution layered cathode material, Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂, was synthesized using a fast co-precipitation method, and surface modified withAg/C via chemical deposition. The electrochemical properties, structures, and morphologies of the prepared samples were investigated using X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), galvanostatic charge-discharge cycling, cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and energy dispersive X-ray spectroscopy (EDS). The XRD results showed that the pristine and Ag/Ccoated cathode materials both have hexagonal α-NaFeO₂ layered structures with the R3m space group. Microscopic morphological observations and EDS elemental mapping showed that a uniform Ag/C coating layer of thickness 25 nm was deposited on the surfaces of Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ particles. The Ag/C-coated Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ material gave an excellent electrochemical performance. The initial discharge capacity (0.05C) of the Ag/C- coated sample was 272.4 mAh ·g^-1, with an initial coulombic efficiency of 77.4%, corresponding to 242.6 mAh·g^-1 for the pristine sample, with an initial coulombic efficiency of 67.6%, in the potential range 2.0-4.8 V (vs Li/Li⁺). After 30 cycles (0.2C), the Ag/C-coated Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ retained a capacity of 222.6 mAh·g^-1, which was 14.45% higher than that of Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂. We also found that the Ag/C coating improved the rate capability of the solid-solution material Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂. The capacity retention (1C) of the Ag/C-coated sample was 81.3%, compared with the capacity at 0.05C. CV and EIS results showed that the Ag/C coating layer suppressed the oxygen release in the initial charge progress and lowered the surface film resistance and electrochemical reaction resistance of the pristine sample.

This work focused on the electrochemical behavior of Nd(Ⅲ) and the formation of Zn-Nd alloys on Mo electrodes in LiCl-KCl-ZnCl₂ molten salt system at 773 K. Cyclic voltammetry, open-circuit chronopotentiometry, and square-wave voltammetry were used. The results showed that the underpotential deposition of Nd on a predeposited Zn cathode gave three types of Zn-Nd intermetallic compounds in LiCl-KCl-ZnCl₂ solutions. Based on the electrochemical results, square-wave voltammetry was used to determine the concentration changes of Nd during potentiostatic electrolysis. The extraction efficiency of Nd was evaluated based on the concentration changes after electrolysis. The results indicated that the concentration of Nd(Ⅲ) was close to zero, and the extraction efficiency was 99.67% after potentiostatic electrolysis at -1.84 V for 50 h. The extraction of Nd and preparation of Zn-Nd alloys were performed by galvanostatic electrolysis at 973 K. The phase compositions and microstructures of the alloys were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). XRD showed that Nd₂Zn₁₇, LiZn, and Zn phases were present in the alloys. The EDS results indicated that the concentration of Nd in the alloys reached 14.99%.

Monodispersed PtNi nanoparticles were synthesized by galvanic displacement reaction and chemical reduction. The monodispersed PtNi nanoparticles demonstrate, by cyclic voltammetry, enhanced electrocatalytic properties for CO oxidation in 0.1 mol·L^-1 H₂SO₄ solution compared with bulk Pt electrode. In situ electrochemical Fourier transform infrared (FTIR) spectroscopy using CO as the probe molecule was studied. The CO adsorbed on either the PtNi/GC (glassy carbon) electrode or PtNi/Au electrode exhibits characteristics of a symmetric bipolar IR feature with a strong enhancement factor. The results of this paper contribute to the understanding of the special properties and origin of the anomalous IR properties of lowdimensional nanomaterials.

Alloy 800 is an important steamgenerator material used in nuclear power plants, and so there is significant interest in the properties of passive films of this alloy under service conditions. In this work, the semiconductivity of Alloy 800 in sulfate and chloride solutions was investigated using Mott-Schottky analysis, electrochemistry impedance spectroscopy (EIS), scanning electron microscopy (SEM), and scanning electrochemical microscopy (SECM). The Mott-Schottky results show that the semiconductivity is affected by the sulfate to chloride concentration ratio; p-type semiconductivity is exhibited at high concentration ratios but transitions to n-type when the concentration ratio is low. EIS, SEM, and SECM results indicate that the degradation formof the passive filmchanges fromtranspassive dissolution to pitting as the concentration ratio decreases while the film's surface reactivity increases, an effect that is related to the semiconductivity conversion. The observed variation in semiconductivity results fromthe competitive adsorption of sulfate and chloride, a process that modifies the potential drop at the film/solution interface, changes the vacancy types and ultimately determines the semiconductivity.

Reduced graphene oxide/sulfur (RGO/S) composites were synthesized by a one-step hydrothermal method using a mixture of sodium thiosulfate (Na₂S₂O₃) and graphene oxide (GO) solution reacting under acid conditions. We explored the influence of the hydrothermal temperature, reaction time, and sulfur content on the composites. Analysis by X-ray diffraction (XRD), scanning electron microscope (SEM), and the galvanostatic charge and discharge shows that the composites have excellent cycling performance when synthesis occurs at 180 ℃ for 12 h to provide a carbon:sulfur mass ratio of 3:7. The first discharge capacity is delivered at 931 mAh·g^-1 and it remains at 828.16 mAh·g^-1 after 50 cycles. The coulomb efficiency of the composites is above 95%. In addition, the rate capability of these composites is much better than that of sulfur. Sulfur molecules can be evenly distributed between the graphene layers and fixed to the functional groups on the surface of graphene by this one-step hydrothermal method.

We report on an ammonia-evaporation-induced synthetic method for nanostructured LiNi_1/3Co_1/3Mn_1/3O₂ cathode material. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high- resolution transmission electron microscopy (HRTEM), energy- dispersive X- ray spectroscopy (EDS), Brunauer-Emmett-Teller nitrogen sorption, and galvanostatic charge-discharge tests were applied to analyze the crystal structure, micromorphology, and electrochemical properties of nanostructured LiNi_1/3Co_1/3Mn_1/3O₂. The results show that it has a well-ordered layered α-NaFeO₂ with little cation mixing. Awalnutkernel- like morphology is formed by nanosheets, leading to a nanoporous material. The lateral plane of nanosheets are {010}-faceted, which could provide multiple channels for Li⁺-ion migration. The electrochemical properties of the lithium cells used this material as cathode are excellent: the specific discharge capacity at 0.5C,1C, 3C, 5C and 10C is, respectively, up to 172.90, 153.95, 147.09, 142.16, and 131.23 mAh·g^-1 between 3.0 and 4.6 V at room temperature. These excellent features will make the nanostructured LiNi_1/3Co_1/3Mn_1/3O₂ become a positive electrode material of potential interest for useful applications, such as in electric vehicles and hybrid electric vehicles.

The pH of the solution used to produce an electro- polymerized polypyrrole (PPy) film has a significant impact on the morphology and properties of the resulting film and, by extension, on the electrocatalytic activity of the film for the I^-/I₃^- redox reaction. Accordingly, the performance of dye-sensitized solar cells (DSSCs) based on PPy counter electrodes (CEs) is affected by solution pH. In this study, p-toluene sulfonate ion-doped PPy (PPy-TsO) CEs on fluorine-doped tin oxide (FTO) glass substrates were fabricated using an electrochemical method under a constant bias in solutions with various pH values. The effect of the pH of the synthetic solution on the morphology, structure, and electrocatalytic activity during the I^-/I₃^- redox reaction of the obtained PPy CEs was thoroughly investigated by scanning electron microscopy (SEM), UV-Vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). A pH value of 2.0 was found to represent the optimal value, since the PPy-TsO film produced at this pH exhibited the highest degree of doping, the longest conjugation length, and the highest catalytic activity. When working as the CE of a DSSC, this film also showed the highest power conversion efficiency. Films synthesized at pH values either above or below 2.0 exhibited inferior properties and lower performance when in DSSCs.

To improve the light-to-electric conversion efficiency of quantum dots-sensitized nanocrystalline thin-film solar cells, a PbS electrode with high electrocatalytic activity toward polysulfide electrolyte was prepared by successively treating Pb foil in acid and polysulfide solutions. Electrochemical impedance spectroscopy (EIS) measurements were performed to evaluate the electrocatalytic activity of the prepared PbS electrode. Based on the EIS results, the temperature and time to treat the Pb foil in the acid solution were optimized. The PbS electrode prepared under the optimized conditions was used as a counter electrode to fabricate a quantumdotssensitized solar cell with a CdSe quantum dots-sensitized TiO₂ nanocrystalline thin film as the photoanode and polysulfide solution as the electrolyte. Both the electrocatalytic activity and light-to-electric conversion properties of the PbS electrode prepared from acid treatment of Pb foil for the optimized temperature and time are superior to those of electrodes prepared by other reported methods. In our method, the treatment time is considerably less but the PbS counter electrode maintains a superior catalytic activity compared with other methods. X-ray diffraction and scanning electron microscopy were performed to demonstrate the formation process of PbS, and the catalytic enhancement mechanism of the prepared PbS electrode is discussed.

Pt/cobalt-polypyrrole-carbon (Co-PPy-C)-supported catalysts were successfully prepared by pulse-microwave assisted chemical reduction. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques were used to characterize the catalyst microstructure and morphology. The electrocatalytic performance, kinetic characteristics of the oxygen reduction reaction (ORR), and durability of the catalysts were measured by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques. It was found that the particle size of Pt/Co-PPy-C was about 1.8 nm, which was smaller than that of commercial Pt/C (JM) catalysts (2.5 nm). The metal particles were well-dispersed on the carbon support. The electrochemical specific area (ECSA) of Pt/Co-PPy-C (75.1 m²· g^-1) was much higher than that of Pt/C (JM) (51.3 m²·g^-1). The results of XPS showed that most of the Pt in the catalysts was in the Pt(0) state, and XRD results showed that the form of Pt was mainly the facecentered cubic lattice. The Pt/Co-PPy-C catalyst had the same half-wave potential as Pt/C (JM) and showed higher ORR activity. The Pt/Co-PPy-C catalyst proceeded by an approximately four-electron pathway in acid solution. After 1000 cycles of CV, the ECSA attenuation rates of Pt/Co-PPy-C and Pt/C were 13.0% and 24.0% respectively, which means that the Pt/Co-PPy-C catalyst has higher durability. The high performance of Pt/Co-PPy-C makes it a promising catalyst for proton exchange membrane fuel cells.

Nitrogen-doped reduced graphene oxide materials (N-RGO) derived from pyrolysis of graphene oxide (GO)/polyaniline composites were used as a support for the immobilization of Pt nanoparticles. The morphologies and structures of N-RGO and Pt/N-RGO were comprehensively characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. The electrocatalytic activities of the as-prepared catalysts for CO stripping and methanol oxidation were investigated by cyclic voltammetry and chronoamperometry. The results showed that GO was reduced to multilayer graphene by thermal annealing accompanied with successful incorporation of N atoms into RGO. Moreover, the presence of the doped N atoms enhanced the surface defects and electrical conductivity of the RGO materials. Pt nanoparticles on N-RGO were more evenly dispersed, had better CO tolerance, and had higher activity/stability for methanol oxidation than those on RGO without N doping.

Nitrogen-doped mesoporous carbons (NMCs) were synthesized by direct carbonization of zeolitic imidazolate framework-8 (ZIF-8) nanopolyhedrons. The surface morphology and structure were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and surface area and pore size analyzer. The electrochemical supercapacitive properties of the NMCs were also investigated. The results showed that the NMCs had a uniformmorphology, mesoporous nanostructure, and high surface area (2737m²·g^-1). On the other hand, based on the excellent surface wettability, pseudocapacitive behavior and electrolyte accessibility resulted fromN-doping and the mesoporous structure, the NMCs exhibited excellent electrochemical supercapacitive properties: a high specific capacitance (307 F·g^-1 in 1.0 mol·L^-1 H₂SO₄ solution, at 1 A·g^-1), good power characteristics, and satisfactory stability (the capacitance retained ratio was 96.9%after 5000 cycles even at a high current density of 10A·g^-1).

Tin has a theoretical specific capacity as high as 990 mAh·g^-1, and is thus a potential anode material for high-energy-density lithium-ion batteries. However, it suffers from a huge volume change during lithiation/delithiation process, leading to poor cycle performance. In this paper, core/shell structured FeSn₂-C composites were successfully synthesized by a simple high-energy ball milling technique with Sn, Fe, and graphite powder as raw materials. The FeSn₂-C composite was evaluated as an anode material for lithium-ion batteries. The influence of milling time and final phase composition on the microstructure and electrochemical performance of FeSn₂-C composites was systematically investigated. The failure mechanism of the FeSn₂-C electrode was also analyzed. The results reveal that long milling time can promote the mechanical alloying process of the FeSn₂ phase and reduce the particle size of the FeSn₂-C composite, which are beneficial for the increase of the specific capacity and the improvement of the cycle performance of the FeSn₂-C electrode. A high FeSn₂ phase content leads to a high specific capacity of the FeSn₂-C composites but poor cycling stability of the electrode. The optimized Sn₂₀Fe₁₀C₇₀ composite prepared by ball milling for 24 h (500 r ·min^-1) shows the best electrochemical performance with a capacity about 540 mAh·g^-1 for 100 cycles. The synthesized Sn₂₀Fe₁₀C₇₀ composite is a promising anode material for highenergy-density lithium-ion batteries.

The effects of HF treatment on the photoelectrochemical (PEC) properties of sol-gel prepared hematite (α-Fe₂O₃) thin films were investigated. Pores and interstices between the grains developed on the film surface as the HF etching time increased. The photocurrent density of the α-Fe₂O₃ photoanode decreased within the first 5 min of etching, and then increased quickly as the etching time increased. At longer time than 15 min the photocurrent density deteriorated. Re-annealing the etched samples significantly enhanced the photocurrent density. Based on electrochemical impedance spectroscopy, Raman and X-ray photoelectron spectroscopies, we propose that two factors contribute to photocurrent density reversely: the porosity and the lowered crystallinity of the α-Fe₂O₃ surface because of HF treatment.Aschematic model was compiled to explain the enhanced PEC activities of the etched plus re-annealed α-Fe₂O₃ photoanode. The PEC and water splitting measurements showed that the etched plus re-annealed photoanode is more stable than the as-prepared one.

Mesoporous TiO₂ microspheres (MSs) were successfully synthesized by the direct hydrolysis of TiCl₄ in ethanol aqueous solution using cetyltrimethyl ammonium bromide (CTAB) as a template. X-ray diffraction (XRD) revealed a rutile structure for TiO₂ in all the products. Scanning electron microscopy (SEM) revealed that the TiO₂ microspheres had an average diameter of 700 nm, and they were composed of packed nanoparticles that had a mean size of about 16 nm. Films with or without TiO₂ microspheres, as a scattering layer on top of the TiO₂ nanocrystalline layer, were prepared by the doctor-blade method. CdS/ CdSe quantum dots (QDs) were grown on films by chemical bath deposition (CBD) to form QD sensitized solar cells (QDSCs). Ultraviolet-visible and diffuse reflectance spectra showed that these micro-spherical structures were favorable for the deposition of QDs and a relatively higher light scattering effect was observed. This effectively enhanced light harvesting and led to an increase in the photocurrent of the QDSCs. As a result, a power conversion efficiency of 4.5% was obtained, which is 27.7% higher than that of QDSCs without scattering layers and 10.2% higher than that of QDSCs with traditional scattering layers composed of 20 and 400 nm TiO₂ solid particles. We attribute this improvement to their higher light scattering effect and longer electron lifetimes.

We report the synthesis of a novel multiwalled carbon nanotube-Na₃V₂(PO₄)₃ (MWCNT-NVP) composite with excellent electrochemical performance. The composite material was prepared by a hydrothermal process combined with a sol-gel method. The MWCNT-NVP composite consists of Na₃V₂(PO₄)₃ (NVP) and a small amount of multiwalled carbon nanotubes (MWCNTs) (8.74%(w)). The MWCNTs were successfully dispersed between the NVP nanoparticles, which was confirmed by field-emission scanning electron microscopy, and served as a kind of "electronic wire". Electrochemical measurements show that the MWCNTNVP composite has enhanced capacity and cycling performance compared with pristine Na₃V₂(PO₄)₃. At a current rate of 0.2C (35.2 mA·g^-1), the initial reversible discharge capacity of the MWCNT-NVP was 82.2 mAh·g^-1, and 72.3 mAh·g^-1 was maintained after 100 cycles when cycled between 3.0 and 4.5 V. Good cycling performance was also observed when cycling between 1.0 and 3.0 V. The initial reversible capacity was 100.6 mAh·g^-1 and the capacity retention was 90% after 100 cycles. Additionally, electrochemical AC impedance showed that the electronic conductivity of MWCNT-NVP was significantly improved in the presence of the MWCNTs. These results indicate that the MWCNT-NVP composite has outstanding properties, and is thus a promising alternative for lithium-ion batteries with relatively low lithium consumption.

For advanced performance lithium-ion batteries (LIBs) various novel electrode materials with high energy density have been extensively investigated. Cobaltosic oxide (Co₃O₄), commonly used as an anode in LIBs, has attracted much interest because of its high theoretical specific capacity (890 mAh·g^-1), high tap density, and stable chemical properties. However, its practical use has been hindered because of its low electronic conductivity and poor rate capability. To address these problems, we investigated a liquid phase precipitation method followed by thermal treatment and obtained a unique lamellar Co₃O₄ powder. Its X-ray diffraction (XRD) diffraction peaks match the standard pattern for cubic phase Co₃O₄ with good crystallinity. We found that the Co₃O₄ powder consists of many irregular sheets (1.5-3.0 μm in diameter, 100-300 nm in thickness) with numerous poles by scanning electronmicroscopy (SEM).Additionally, the surface area was about 30.5 m²·g^-1, and this was calculated from BET nitrogen adsorption isotherm measurement data. Remarkably, perfect performance was obtained as evaluated by electrochemical measurements, including a high initial discharge capacity (1444.5 mAh·g^-1 at 0.1C) and excellent capacity retention (charge capacity after 50 cycles was still greater than 1100.0 mAh·g^-1 at 0.1C). However, its rate capability was still not adequate (75.3% of the first charge capacity after 50 cycles at 1C). To improve the rate capability, commercial carbon nanotubes (CNTs) mixed with the Co₃O₄ powder was used to enhance the electronic conductivity. The charge capacity retention ratios were 96.3% after 70 cycles at 1C and 97.0% after 50 cycles at 2C. Therefore, enhanced electrochemical performance with impressive rate capability was obtained, as expected.

B/N co-doped porous carbons have been synthesized by heat treatment at different temperatures using asphaltene from coal liquefaction residue as a carbon precursor, nitric acid as a nitrogen source, H₃BO₃ as a boron source and a pore-forming agent. The influence of the heat treatment temperature on the porestructure and surface chemical properties was investigated, and the electrochemical performance in relation to the pore-structure and surface chemical properties was discussed. The crystal structure, morphology, porestructure, composition and electrochemical performance were examined using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, element analysis, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), and an electrochemical workstation. The results of these analyses indicated that the crystal structure, pore-structure and surface properties were influenced significantly by the heat treatment process. Increases in the heat treatment temperature led to improvements in the degree of graphitization, as well as gradual increases in the boron content. In contrast, the nitrogen content decreased and the specific surface area and total pore volume increases gradually and then decline. The electrochemical performance was found to be dependent on the pore-structure and suitable surface chemical properties. The sample synthesized at 900 ℃ had a specific surface area of 1103 m²·g^-1, pore volume of 0.921 cm³·g^-1, nitrogen content of 5.256% (w), boron content of 1.703% (w), and a maximal specific capacitance of 349 F·g^-1 at 100 mA·g^-1 in 6 mol·L^-1 aqueous solution of KOH. The sample subjected to a heat treatment at 1000 ℃ had the best rate capability, with a capacity retention of 75% when the current density increased from 100 mA·g^-1 to 10 A·g^-1.

A vacuum-assisted precipitation method was used to synthesize Fe₃(PO₄)₂·8H₂O (FP). The FP was then used to synthesize carbon-coated LiFePO₄ (LFP/C) particles. The influence of FP on the structure, morphology, and electrochemical performance of LFP was investigated. The X-ray diffraction (XRD) patterns and molar ratio of Fe to P showed that the FP which was produced using a vacuum-assisted method was of high purity and gave highly crystalline, impurity-free LFP. Scanning electron microscopy (SEM) showed that the FP contained undeveloped particles. The undeveloped FP results in uniform LFP/C particles, without agglomeration. Transmission electron microscopy (TEM) showed that the LFP particles were coated with a homogeneous carbon layer. The LFP/C showed excellent discharge capacities of 140, 113, and 100 mAh·g^-1 at 1C, 10C, and 20C rates, respectively. The cyclic voltammograms (CVs) of LFP showed a low polarization voltage and sharp redox peaks. The charge-discharge platform curves showed that LFP had an excellent high-rate capability. Electrochemical impedance spectroscopy (EIS) tests showed that the lithium-ion diffusion coefficients of LFP/C produced with and without vacuum assistance were 1.42×10^-13 and 4.22×10^-14 cm²·s^-1, respectively, proving that vacuum assistance can improve the diffusion coefficients of LFP/C.

Single-crystal TiO₂ nanorod arrays (TNRs) are proposed to increase the electron transport rate and improve the cell performance of quantum dot- sensitized solar cells (QDSCs). However, the specific surface area of TNRs is much lower than that of TiO₂ nanoparticle films, which leads to lower quantum dot adsorption and lower power conversion efficiency (η). In our investigation, TiCl₄ solution was used to modify single-crystal rutile TNRs. The modification resulted in the synthesis of a large number of TiO₂ nanoparticles on the surfaces of nanorods, which significantly increased the surface area and quantum dot adsorption of TNRs. When the TiCl₄ modification time was 60 h, the short-circuit photocurrent density (J_sc) and η of TNRs based CdS/CdSe co-sensitized QDSCs increased from (2.93±0.07) mA·cm^-2 and 0.36%±0.02% to (8.19±0.12) mA·cm^-2 and 1.17%±0.07%, respectively. In addition, intensity modulated photocurrent spectroscopy measurements indicated that the electron transport rate in modified single-crystal rutile TNRs is faster than that in anatase TiO₂ nanoparticle films, which is a desirable result.

This article describes the electrochemical performance of a novel interconnected porous carbon/ MnO₂ (IPC/MnO₂) composite prepared by in situ self-limiting deposition under hydrothermal condition. The morphology and structure were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA), and the electrochemical behavior was investigated using cyclic voltammetry (CV), charge-discharge tests, electrochemical impedance spectroscopy (EIS), and cycle life tests. The results showed that MnO₂ grew homogeneously on the IPC surface, forming a hierarchical microstructure. The MnO₂ had a typical K-Birnessite-type crystal structure and the MnO₂ content was about 34%(w). At high synthetic temperatures, the MnO₂ particles on the IPC surface were smaller. The prepared electrode material exhibited a good electrochemical capacitance performance. As the reaction temperature increased, the specific capacitance of the IPC/MnO₂ composite first increased and then remained constant. The IPC/MnO₂ composite synthesized at 100 ℃ had the maximum specific capacitance, 411 F·g^-1, in a three-electrode system. An asymmetric supercapacitor was constructed with the IPC/MnO₂ composite as the positive electrode and activated carbon (AC) as the negative electrode, in a 1 mol·L^-1 Na₂SO₄ electrolyte. The results showed that the corresponding potential window increased from 1 to 1.8 V. The maximum specific capacitance of the asymmetric supercapacitor was 86 F·g^-1 and a good rate capability was achieved.

A tungsten carbide and tungsten-iron carbide composite with a core-shell structure was prepared through a combination of surface coating and in situ reduction-carbonization, using ammonium metatungstate as the tungsten source and iron hydroxide as the iron source. The main crystal phases of the composite were tungsten-iron carbide (Fe₃W₃C), monotungsten carbide (WC), and bitungsten carbide (W₂C). In the core-shell composite, Fe₃W₃C formed the core, and the shell consisted of WC and W₂C. The electrocatalytic activity for methanol oxidation of the composite was measured by cyclic voltammetry with a three-electrode system in acidic, neutral, and alkaline aqueous solutions. The results show that the electrocatalytic activity of the composite is higher than those of tungsten carbide particles and mesoporous hollow microspheres. The activity is affected by the properties of the solution in which the reaction is performed, and is related to the crystal phase and microstructure of the composite. These results indicate that the electrocatalytic activity of tungsten carbide can be adjusted by changing the properties of the reaction solution and controlled by adjusting the crystal phase and microstructure of the composite. Furthermore, the activity can be improved through formation of a core-shell structure; this is an efficient way to improve the electrocatalytic activity of tungsten carbide.

A hetero-layered MnO₂/NiCo₂O₄ composite was fabricated according to an electrostatic self-assembly process between negatively charged MnO₂-layered nanosheets and positively charged Co-Ni-layered double hydroxide nanosheets, followed by a heat-treatment process. The morphology, composition, and microstructure characteristics of the resulting material were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectrometry, atomic absorption spectrometry (AAS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Furthermore, the electrochemical behaviors of the composite were evaluated by cyclic voltammetry (CV), galvanostatic chargedischarge, and electrochemical impedance spectroscopy (EIS). The test results indicated that the hetero-layered composite showed porous stacking structure, which increased the effective liquid-solid interfacial area, and provided a fast path for the insertion and extraction of electrolyte ions. A specific capacitance of 482 F·g^-1 was obtained in the potential window from-0.6 to 0.45 V at a current density of 1 A·g^-1. These values were therefore superior to those of pure MnO₂ or pure NiCo₂O₄.

The modification of a TiO₂/dye/electrolyte interface can effectively improve the performance of dyesensitized solar cells (DSCs). A variety of methods has been reported for the modification of this interface, among which the introduction of a small organic molecule co-adsorbed with the dye on the surface of TiO₂, which is simple and effective. In this paper, di-n-dodecylphosphinic acid (DDdPA) was synthesized and used as a coadsorbent in a Z907 based dye-sensitized solar cell. Its good adsorption property on the surface of TiO₂ film containing Z907 was confirmed by Fourier transform infrared (FT-IR) spectroscopy. The dynamic processes of electron transport and recombination were investigated by electrochemical impedance spectroscopy (EIS) and intensity-modulated photocurrent spectroscopy (IMPS)/intensity-modulated photovoltage spectroscopy (IMVS). Compared with the widely used bis-(3,3-dimethyl-butyl)-phosphinic acid (DINHOP) coadsorbent, the DSC based on DDdPA is more effective in reducing electron recombination as shown by the EIS measurement, and this is mainly owed to the longer alkyl chain and the more pronounced steric hindrance effects. With an optimized concentration ratio of Z907 to DDdPA of 2:1, the charge transfer resistance (R_ct) is larger than that of the device with only Z907 and an optimized Z907-to-DINHOP ratio of 1:1. IMPS/IMVS measurements indicate that the introduction of DDdPA effectively enhances the electronic lifetime and leads to a negative shift of about 30 mV for the conduction band edge. With the optimized DDdPA concentration, the open-circuit photovoltage (V_oc) improved by 47 mV, and the power conversion efficiency of the DSC improved by 10%.

This research developed a novel composite co-precipitation method to prepare high performance LiNi_0.5Mn_1.5O₄ based on a traditional solid-state method. Ammonium oxalate/ammonium carbonate was used as a composite precipitator to deposit Ni/Mn ions. Combined with a facile hydrothermal treatment, stoichiometric LiNi_0.5Mn_1.5O₄ was obtained with a pure spinel structure and spherical hierarchical morphology. Electrochemical measurements indicate that the as-prepared LiNi_0.5Mn_1.5O₄ delivers a high capacity of 141.4 mAh·g^-1 and after 200 cycles under 0.3C, 1C, and 3C, the materials retained their capacities up to 96.3%, 94.4%, and 91.1%, respectively. Additionally, the capacity upon exposure to a low voltage of 4.0 V was efficiently eliminated by heat treatment and by a particular cooling process. Furthermore, the LiNi_0.5Mn_1.5O₄ materials with high energy and high power performances of 648.6 mWh·g^-1 and 7000mW·g^-1 were obtained because of different cation ordering.

The synergistic inhibition effect of the imidazoline ammonium salt (IAS) and sodium dodecyl sulfate (SDSH) on the corrosion of Q235 carbon steel in a CO₂ saturated brine solution was studied by weight loss, electrochemical impedance spectroscopy (EIS), Tafel polarization measurements, X-ray photoelectron spectrometry (XPS), and scanning electron microscopy (SEM). We found that in the CO₂ saturated brine solution, a good synergistic inhibition effect exists between IAS and low concentrations of SDSH, and the most significant synergistic inhibition occurred at a concentration ratio of 1:1 (50 mg·L^-1:50 mg·L^-1) with an inhibition efficiency of 88.5%. However, antagonism occurs upon mixing IAS with a high concentration of SDSH. In this paper, the mechanisms of the synergistic and antagonistic effects are analyzed using a reasonable adsorption model. Good corrosion inhibition on Q235 carbon steel was also found when only using a high concentration of SDSH with an inhibition efficiency of about 90%. Both the adsorption processes of SDSH and IAS on the surface of Q235 carbon steel are spontaneous processes and the former process complies with the Frumkin adsorption model while the later complies with the Temkin adsorption model.

Based on the reaction mechanism of the electro-oxidation of sulfide on platinum, we propose a simplified model for studying the spatiotemporal dynamics on the electrode surface in the oscillatory region of the N-shaped negative differential resistance (N-NDR) through numerical simulation. Simple and complex current oscillations were observed during the homogeneous simulation, and these were caused by coupling between one positive feedback, i.e., double-layer potential autocatalysis, and two negative feedbacks consisting of a mass-transport limited step and a poison-adsorption process. To obtain a better simulation of the experimental situation, the transport of electroactive species in both the parallel and vertical directions of the electrode was taken into account to simulate pattern formation on the electrode. The model simulations gave complicated patterns including twinkling-eye patterns and traveling waves, which agree qualitatively with the experimental results and possess the same evolution principles. Meanwhile, for certain parameters more complex patterns were obtained, e.g., two-arm spiral waves of the double-layer potential. This opens an interesting perspective in the explanation and prediction of pattern formation in electrochemical systems.

An efficient front-illuminated dye-sensitized solar cell (DSSC) based on ordered TiO₂ nanotube (TNT) arrays was prepared. Sintering at 450 ℃ avoided damage of the ordered TNTs during HF treatment. Fast electron transport channels were maintained in the membrane, for efficient charge transportat in the DSSC. The sintered TNT membranes were subsequently treated with HF, TiCl₄, and HF combined with TiCl₄. This formed a rougher surface, and allowed increased dye loadings. The increased dye loading improved the light harvesting efficiency of the photoanode at 300-570 nm wavelength range, which is the main absorption region of the adsorbed dye. The adsorbed dye had a low absorption at 570-800 nm wavelength range. The enhanced light harvesting efficiency of the photoanode originated from its increased diffuse reflectance. The incident-photon-to-current and absorbed-photon-to-current conversion efficiencies were increased over the entire 300-800 nm wavelength range. This resulted in an increased short-circuit current density of the DSSC. Electrochemical impedance spectroscopy indicated that electron transport and related parameters including charge transport resistance, interfacial charge recombination resistance, distributed chemical capacitance, electron lifetime, effective electron diffusion length, and collection efficiency were significantly improved in the DSSC containing the treated TNT photoanode. This also resulted in an enhanced photovoltaic performance. The maximum power conversion efficiency from combining HF and TiCl₄ treatments was 7.30%, which was a 35.69% enhancement compared with the nontreated DSSC (5.38%).

The efficiency of bulk heterojunction solar cells was enhanced by incorporating CdSe/ZnS core-shell colloidal quantum dots (CQDs) into copolymers of poly(3-hexylthiophene (P3HT) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) as the active layer, as result of the increased absorption in the visible region. The doping of CdSe/ZnS CQDs in the active layer and the influence of CQD surface ligands on device performance were investigated. A maximum power conversion efficiency (PCE) of 3.99% was obtained from the optimized solar cell ITO/PEDOT:PSS/P3HT:PCBM:(CdSe/ZnS)/Al (ITO: indium-tin oxide; PEDOT: poly(3,4-ethylendioxythiophene; PSS: poly(styrenesulfonate)) under AM1.5 illumination. This was 45.1% improvement on the PCE of the control device ITO/PEDOT:PSS/P3HT:PCBM/Al.

Nano-LiMnPO₄ samples were synthesized via a two-step heating polyol method. The role of the first thermal plateau temperature T₁ (T₁=100, 110, 120, 130, 140, 150 ℃) on the physical and electrochemical properties of the samples was investigated. Their structures and morphologies were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and N₂ sorption measurements. All samples at different plateau temperatures exhibited a sheet structure. At T₁=100-120 ℃, samples contained some impurities, and their specific surface areas were <15 m²·g^-1. Pure nano-LiMnPO₄ was obtained at T₁=130 ℃, and exhibited the largest specific surface area (46.3 m²·g^-1). The specific surface areas of samples remained at 35-37 m²·g^-1 with further increase in T₁. The electrochemical performance of the nano-LiMnPO₄ samples followed the same trend as their specific surface areas. Nano-LiMnPO₄ at T₁=130 ℃ exhibited the best electrochemical performance, with a discharge capacity of 129 mAh·g^-1 at 0.1C rate and 81 mAh·g^-1 at 5C rate. This indicated that the specific surface area is one of the key factors in determining the electrochemical performance of LiMnPO₄.

A series of lithium-rich cathode materials, xLi₂MnO₃·(1-x)LiNi_0.5Mn_0.5O₂ (x=0.1-0.8), were successfully synthesized by a sol-gel method. X-ray diffraction, scanning electron microscopy, and electrochemical tests were used to investigate the crystal structure, morphology, and electrochemical performance of the as-synthesized materials, respectively. The results showed that the materials with higher Li₂MnO₃ content had higher initial discharge capacity but poorer cycle stability, while the materials with lower Li₂MnO₃ content showed lower discharge capacity but better cycle stability, and the spinel impurity phase was also found. Based on the data, the optimal electrochemical properties were obtained when x=0.5 in xLi₂MnO₃·(1-x)LiNi_0.5Mn_0.5O₂. Moreover, the electrochemical properties were also worthy of attention when x=0.4, 0.6.

WO₃ nanorods/graphene nanocomposites (WO₃/RGO) were prepared by the solvothermal treatment of tungsten hexachloride and graphene oxide in alcohol. The electrochemical performance of WO₃/RGO as anode materials for lithium-ion batteries was investigated by galvanostatic charge-discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The discharge capacity of the composite at the first cycle was 761.4 mAh·g^-1, and about 635 mAh·g^-1 of reversible capacity remained after 100 cycles at a rate of 0.1C (1C=638 mA·g^-1). The corresponding retention rate was 83.4%. The reversible capacity remained lager than 460 mAh·g^-1 at a rate of 5C. WO₃/RGO exhibited excellent cycling stability and rate performance, and has potential in advanced lithium-ion batteries.

Separators are important components in electrochemical energy storage devices such as electrical double layer capacitors (EDLCs) and hybrid battery-supercapacitors. We prepared activated carbon-based EDLCs using an electrolyte of 1 mol ·L^-1 tetraethyl ammonium tetrafluoroborate (Et₄NBF₄) in propylene carbonate (PC), and (LiNi_0.5Co_0.2Mn_0.3O₂+activated carbon)/graphite hybrid battery-supercapacitors using a 1 mol·L^-1 lithium hexafluorophate (LiPF₆) Li-ion electrolyte. The physicochemical properties and effect of various separators on the electrochemical properties of the EDLC and hybrid battery-supercapacitor were studied. The four separators were nonwoven polypropylene (PP) mat, porous PP membrane, Al₂O₃-coated PP membrane, and cellulose paper. The surface morphology, differential scanning calorimetry, electrolyte uptake, and apparent contact angle were investigated. The electrochemical characterizations of coin cells indicated that the EDLC with cellulose separator had the highest specific capacitance and rate capability. Differences in the selfdischarge of the four cells were not obvious. The specific capacities of the hybrid battery-supercapacitors with PP membrane and nonwoven PP mat separators were approximately 20% higher than the others. The capacitor with the cellulose paper separator had the highest self-discharge rate.

Anodic layers and oxygen evolution reaction (OER) of Pb-Ag and Pb-Ag-Nd anodes were investigated by cyclic voltammetry, linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and environmental scanning electron microscopy (ESEM). Alloying with Nd promoted the formation of Pb/PbO_n/PbSO₄ (1≤n<2). Nd facilitated the transformation of PbO_n and PbSO₄ to α-PbO₂ and β-PbO₂, at potential above 1.2 V vs Hg/Hg₂SO₄ (saturated K₂SO₄ solution). ESEM and LSV indicated that the anodic layer formed on the Pb-Ag-Nd anode was thicker and more compact than that formed on the Pb-Ag anode. Consequently, the anodic layer on the Pb-Ag-Nd anode could provide better protection for metallic substrates. EIS indicated that the OER was determined by the formation and adsorption of intermediates. Nd enhanced the OER reactivity, because of a smaller adsorption resistance and larger coverage of intermediates at the anodic layer/electrolyte interface. In summary, alloying with Nd can enhance the corrosion resistance and reduce the energy consumption of Pb-Ag anode due to lower anodic potential.

We designed a series of models of reduced graphene oxide sheets (rGNOs) with different oxidation degrees and then studied the interactions between oxidation defects on rGNOs and nickel hydroxide (Ni(OH)₂) using density functional theory (DFT). The adsorption energy between the oxygen-containing groups on rGNOs and Ni(OH)₂ is dependent on the oxidation degree of rGNOs. The variations of atomic distances and charge distribution of the oxide-defected graphene after absorbing Ni(OH)₂ suggested that the oxygen-containing groups on rGNOs improve the characteristics of Ni(OH)₂ as a pseudocapacitor. These theoretical results agree well with available experimental observations and give an explanation for some experimental results. We also introduce a simple potentiostatic electrodeposition method, with which Ni(OH)₂ nanoparticles about 5 nm in diameter were effectively dispersed on the substrate via induction of oxidation defects on rGNOs. In the fabrication of Ni(OH)₂/rGNOs, electrochemical reduction of graphene oxide is the key process. The stronger adsorption results in Ni(OH)₂/rGNOs have higher rate pseudocapacitance (1591 F·g^-1 at 5 mV·s^-1) compared with that of Ni(OH)₂ on bare nickel (656 F·g^-1 at 5 mV·s^-1). The variations of the geometries and charge distributions of the rGNOs after absorbing Ni(OH)₂ lead to the lower equivalent series resistance and better frequency response of Ni(OH)₂/rGNOs than Ni(OH)₂/Ni. The high capacitance of Ni(OH)₂/rGNOs indicates that Ni(OH)₂/rGNOs have the potential of being used as the electrode material of pseudocapacitors.