Non-precious metal catalysts should be studied to substitute precious Pt catalysts. Recent developments of non-precious-metal catalysts (combined with the achievements of our group) are summarized in this paper. The main issues that exist in the transition metal oxides, metal-nitrogen-carbon material, and heteroatom-doped carbon material are highlighted from the aspects of the synthetic methods and mechanisms. The research tendency and perspective of these non-precious metal catalysts are provided.
Received: 05 December 2016
Published: 09 February 2017
Fund: the National Natural Science Foundation of China(91534205);the National Natural Science Foundation of China(21573029);the National Natural Science Foundation of China(21436003);the National Natural Science Foundation of China(51272297)
Fig 1 (a) Scanning electron microscopy image (SEM) and (b) high magnification transmission electron microscopy (TEM) images of Co3O4/N-rmGO hybrid; (c) C K-edge X-ray absorption near edge structure (XANES) of N-rmGO and Co3O4/N-rmGO hybrid, inset showing O K-edge XANES of Co3O4 and Co3O4/N-rmGO hybrid; (d) oxygen reduction polarization curves of Co3O4/rmGO, Co3O4/N-rmGO and a high quality commercial Pt/C catalyst14catalyst loading: 0.24 mg·cm-2
Fig 2 (a) Relationship between oxygen vacancy (OV) concentration and oxygen reduction reaction (ORR) activity of MnO2(110) surface; (b) changes in the band gap, EHOMO, and EFermi of β-MnO2, EFermi of MnOOH, and O―O bond as a function of the OV concentration20
Fig 3 First-principle study of surface oxygen adsorption on different sites of (a, b) cubic and (c, d) tetragonal spinel phases26
Fig 4 Scheme of structure reversing and dissimilarity effect, and the relationships between ORR activity and Fermi energy or lattice parameters28
Fig 5 Illustration of the synthesis of Fe-N-doped ordered mesoporous carbon catalysts (FeX@NOMC)52
Fig 6 TEM images of hollow micro/meso-pore nitrogen-doped carbon (HMNC) at different Fe contents54(a) HMNC-0-800, (b) HMNC-0.2-800, (c) HMNC-0.5-800, (d) HMNC-0.8-800, (e) HMNC-1.0-800
Fig 7 (a) Shape fixing via salt recrystallization method; (b) steady-state plots (bottom) of ORR polarization and (top) of H2O2 yield for different catalysts in O2-saturated 0.1 mol·L-1 HClO4; (c) polarization curves and corresponding power densities of membrane electrode assemblies fabricated with the CPANI-Fe-NaCl, CPANI-NaCl, and CPANI cathode catalysts55(c) The loading is 50 μg of Pt cm-2 for Pt/C (40% (w)) and is 0.6 mg·cm-2 for non-Pt catalyst.
Fig 8 (a) SEM image of the as-synthesized vertically alligned nitrogen-containing carbon nanotube (VA-NCNTs); (b) TEM image of the electrochemically purified VA-NCNTs; (c) digital photograph of the VA-NCNT array; (d) rotating ring-disk electrode (RRDE) voltammograms for oxygen reduction in air-saturated 0.1 mol·L-1 KOH at the Pt-C supported by a glass carbon electrode (Pt-C/GC) (curve 1), nitrogen-free nonaligned carbon nanotube supported by a glass carbon electrode (VA-CCNT/GC) (curve 2), and VA-NCNT (curve 3) electrodes; (e) calculated charge density distribution for the NCNTs; (f) schematic representations of possible adsorption modes of an oxygen molecule at the CCNTs (top) and NCNTs (bottom)59scale bar: (a) 2 mm; (b) 50 nm
Fig 9 Schematic representation of the common N bonding configurations80
Fig 10 (a) Bandgap vs N doped content for graphitic N-doped graphene (GNG) and pyridinic N-doped graphene (PNG); (b) free energy curves of ORR on GNG and PNG; (c) a novel perspective about the dispute on the contribution of different N-type to ORR activity in N-doped graphene85
Name of catalyst
Content of PNa/%
Content of GNb/%
Table 1Summary of various N-doped carbon material including distribution of different N-doped parttern, and the most active parttern
Fig 11 (a) Schematic of the selectivity inside and outside of montmorillonite (MMT) during nitrogen-doped graphene (NG) synthesis; (b) Bode spectra of different NG material80; (c) ORR polarization for different catalysts in O2-saturated 0.1 mol·L-1 HClO4(b) The sine wave with an amplitude of 5.0 mV from 10 MHz to 10 kHz is applicated for different catalysts.
Quaternary and oxidizde N/%
Specific area/ (m2·g-1)
jk/(mA·cm-2) (at 0.7 V)
between MMT particles
Table 2X-ray photoelectron spectroscopy (XPS) data and RRDE results for nitrogen doped carbon with different conditions
Fig 12 Schematic of the effective utilization of N-containing active sites; (b) the Bode spectra with different catalysts; (c) capacitance-eliminated linear sweep voltammetry (LSV) results for different catalysts (b) through the application of a sine wave with amplitude of 5.0 mV from 10 mHz to 10 kHz for bulk nitrogen-doped carbon (NC), CNT@NC and NC + CNTs. (b) The inset is the simple illustration of the homemade button cell. (c) scan rate:10 mV·s-1, rotation speed:1600 r·min-1. The catalyst loadings are 0.6 mg·cm-2 for non-Pt catalysts and 0.026 mg·cm-2 for JM-Pt/C93.
Fig 13 (a) Spin density distributions on perfect graphene cluster with substituting S at the zigzag edge71; (b) spin and charge density of graphene network dual-doped by N and S77(a) The density variation from positive to negative values in the color order of red, orange, yellow, green, and blue. Sulfur atoms is labeled with S; (b) C1 has very high spin density, C2 and C3 have high positive charge density, and C4 and C5 have moderately high positive spin densities. color online
Fig 14 (a) Schematic illustration of fabrication process and structure of the N, P-GCNS bifunctional oxygen electrocatalyst; (b) bifunctional catalytic activity of various catalysts toward both ORR and oxygen evolution reactions (OER)63
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