物理化学学报

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Ni,Co基硒化物修饰g-C3N4光催化产氢研究

靳治良, 李彦兵, 郝旭强   

  1. 北方民族大学 化学与化学工程学院, 宁夏太阳能化学转化技术重点实验室, 国家民委化工技术基础重点实验室, 银川 750021
  • 收稿日期:2019-12-11 修回日期:2020-01-05 录用日期:2020-01-21 发布日期:2020-02-03
  • 通讯作者: 李彦兵, 郝旭强 E-mail:1757039358@qq.com;haoxuqiang@126.com
  • 基金资助:
    国家自然科学基金(21862002,41663012),北方民族大学重大科研项目“清洁能源催化生产中的新技术、新体系”(ZDZX201803)和北方民族大学宁夏低品位资源高价值利用与环境化学一体化技术创新团队项目资助

Ni, Co-Based Selenide Anchored g-C3N4 for Boosting Photocatalytic Hydrogen Evolution

Zhiliang Jin, Yanbing Li, Xuqiang Hao   

  1. School of Chemistry and Chemical Engineering, Key Laboratory for Chemical Engineering and Technology, State Ethnic Affairs Commission, Ningxia Key Laboratory of Solar Chemical Conversion Technology, North Minzu University, Yinchuan 750021, P. R. China
  • Received:2019-12-11 Revised:2020-01-05 Accepted:2020-01-21 Published:2020-02-03
  • Supported by:
    This work was financially supported by the Chinese National Natural Science Foundation (21862002 and 41663012), the New Technology and System for Clean Energy Catalytic Production, Major Scientific Project of North Minzu University (ZDZX201803), the Ningxia Low-Grade Resource High Value Utilization and Environmental Chemical Integration Technology Innovation Team Project of North Minzu University.

摘要: 新型高效的催化剂是突破单体光催化材料载流子低分离和转移效率的重要途径。本文将Ni3Se4和CoSe2纳米粒子锚定在具有良好分散性的g-C3N4纳米片表面,合成了两种新的g-C3N4@Ni3Se4和g-C3N4@CoSe2光催化剂并实现了原位光催化析氢。相当严重的载流子的重组导致g-C3N4单体展现了大约只有1.9 μmol·h-1的极差的光催化析氢活性。Ni3Se4和CoSe2纳米颗粒对于加速载流子快速分离和转移的独特作用使得在g-C3N4表面负载Ni3Se4和CoSe2纳米粒子极大地提高了其产氢活性。G-C3N4@Ni3Se4展示了一个大约16.4 μmol·h-1的光催化产氢活性并且g-C3N4@CoSe2展现了一个大约25.6 μmol·h-1的光催化产氢活性,这分别是g-C3N4单体的8倍和13倍。其中,将Ni3Se4和CoSe2与g-C3N4耦合可以显著提高光吸收密度以及扩展光响应范围。激发态EY在g-C3N4@Ni3Se4和g-C3N4@CoSe2存在时比在g-C3N4存在时展现了更低的荧光强度,并且在g-C3N4@Ni3Se4和g-C3N4@CoSe2体系中可观察到最大的电子转移速率。相比g-C3N4@Ni3Se4@FTO和g-C3N4@CoSe2@FTO电极,g-C3N4@@FTO显现了最小的光电流响应密度和最大的电化学,这表明在g-C3N4纳米片表面引入Ni3Se4和CoSe2纳米颗粒增强了光生载流子的分离和转移效率,即基于g-C3N4的金属硒化的合成有效地抑制了光生载流子的复合以及促进了光催化水裂解制氢反应。同时,吸收带边的红移有效地降低了光激电子从价带到导带跃迁的阈值。此外,g-C3N4@Ni3Se4和g-C3N4@CoSe2复合催化剂的zeta电位比g-C3N4的更负,说明样品表面对质子增强的吸附。并且密度泛函理论结果表明:g-C3N4中N位点对H的吸附能为-0.22 eV,还发现氢原子更倾向于吸附在两个硒原子的桥位点上形成Se―H―Se键,并且吸附能为1.53 eV。所有对样品进行的透射电子显微镜(TEM)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、X射线衍射(XRD)、紫外可见漫反射光谱(UV-Vis-DRS)、瞬态光电流、傅立叶变换红外光谱(FT-IR)等相关表征都展示了彼此匹配的结果。

关键词: Ni3Se4, CoSe2, g-C3N4, 析氢

Abstract: Developing novel and efficient catalysts is a significant way to break the bottleneck of low separation and transfer efficiency of charge carriers in pristine photocatalysts. Here, two fresh photocatalysts, g-C3N4@Ni3Se4 and g-C3N4@CoSe2 hybrids, are first synthesized by anchoring Ni3Se4 and CoSe2 nanoparticles on the surface of well-dispersed g-C3N4 nanosheets. The resulting materials show excellent performance for photocatalytic in situ hydrogen generation. Pristine g-C3N4 has poor photocatalytic hydrogen evolution activity (about 1.9 μmol·h-1) because of the rapid recombination of electron-hole pairs. However, the hydrogen generation activity is well improved after growing Ni3Se4 and CoSe2 on the surface of g-C3N4, owing to the unique effect of these selenides in accelerating the separation and migration of charge carriers. The hydrogen production activities of G-C3N4@Ni3Se4 and g-C3N4@CoSe2 are about 16.4 μmol·h-1 and 25.6 μmol·h-1, which are 8-fold and 13-fold that of pristine g-C3N4, respectively. In detail, coupling Ni3Se4 and CoSe2 with g-C3N4 greatly improves the light absorbance density and extends the light response region. The photoluminescence intensity of the photoexcited Eosin Y dye in the presence of g-C3N4@Ni3Se4 and g-C3N4@CoSe2 is weaker than that in the presence of pure g-C3N4. On the other hand, the upper limit of the electron-transfer rate constants in the presence of g-C3N4@Ni3Se4 and g-C3N4@CoSe2 is greater than that in the presence of pure g-C3N4. Among the g-C3N4@Ni3Se4@FTO, g-C3N4@CoSe2@FTO, and g-C3N4@FTO electrodes, the g-C3N4@FTO electrode has the lowest photocurrent density and the highest electrochemical impedance, implying that the introduction of CoSe2 and Ni3Se4 onto the surface of g-C3N4 enhances the separation and transfer efficiency of photogenerated charge carriers. In other words, the formation of two star metals selenide based on g-C3N4 can efficiently inhibit the recombination of photogenerated charge carriers and accelerate photocatalytic water splitting to generate H2. Meanwhile, the right shift of the absorption band edge effectively reduces the transition threshold of the photoexcited electrons from the valence band to the conduction band. In addition, the more negative zeta potential for the g-C3N4@Ni3Se4 and g-C3N4@CoSe2 catalysts as compared with that for pure g-C3N4 leads to a notable enhancement in the adsorption of protons by the sample surface. Moreover, the results of density functional theory calculations indicate that the hydrogen adsorption energy of the N sites in g-C3N4 is -0.22 eV; further, the hydrogen atoms are preferentially adsorbed at the bridge site of two selenium atoms to form a Se-H-Se bond, and the adsorption energy is 1.53 eV. In-depth characterization has been carried out by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, transient photocurrent measurements, and Fourier transform infrared spectroscopy; the results of these experiments are in good agreement with one another.

Key words: Ni3Se4, CoSe2, g-C3N4, Hydrogen evolution

MSC2000: 

  • O644