化学学报 ›› 2024, Vol. 82 ›› Issue (4): 409-415.DOI: 10.6023/A23120532 上一篇    下一篇

研究论文

氧空位控制BiVO4晶面异质结的磁性和光电催化性能

王国景a,b,*(), 陈永辉a, 张秀芹a, 张俊笙a, 徐俊敏c,*(), 王静c,*()   

  1. a 兰州大学材料与能源学院 兰州 730000
    b 中国矿业大学材料与物理学院 徐州 221116
    c 郑州大学物理学院 教育部集成电路设计与应用国际合作联合实验室 郑州 450001
  • 投稿日期:2023-12-13 发布日期:2024-03-06
  • 基金资助:
    国家自然科学基金(62304094); 甘肃省自然科学基金(22JR5RA484); 中央高校基本科研业务费专项资金(lzujbky-2023-45); 教育部先进材料重点实验室开放课题(AdvMat-2023-2); 河南省高等学校重点科研项目(24A430039); 河南省自然科学基金(242300420310)

Magnetic and Photoelectrocatalytic Properties of BiVO4 Surface Heterojunctions Controlled by Oxygen Vacancies

Guojing Wanga,b(), Yonghui Chena, Xiuqin Zhanga, Junsheng Zhanga, Junmin Xuc,*(), Jing Wangc,*()   

  1. a School of Material & Energy, Lanzhou University, Lanzhou 730000
    b School of Materials Science and Physics, China University of Mining and Technology, Xuzhou 221116
    c International Joint Laboratory for Integrated Circuits Design and Application, Ministry of Education, School of Physics, Zhengzhou University, Zhengzhou 450001
  • Received:2023-12-13 Published:2024-03-06
  • Contact: * E-mail: wanggj@lzu.edu.cn; junminxu@zzu.edu.cn; jingwang3@zzu.edu.cn
  • Supported by:
    National Natural Science Foundation of China(62304094); Natural Science Foundation of Gansu Province in China(22JR5RA484); Fundamental Research Funds for the Central Universities of Ministry of Education of China(lzujbky-2023-45); Fund of Key Laboratory of Advanced Materials of Ministry of Education(AdvMat-2023-2); Key Research Projects of Higher Education Institutions in Henan Province(24A430039); Natural Science Foundation of Henan Province(242300420310)

在铁磁光催化剂中, 大多数光生电荷具有相同的自旋状态, 因此可以有效抑制光生电子和空穴的复合. 利用BiVO4 {010}和{110}晶面中氧空位的形成能不同, 通过晶面取向和氧空位的协同作用来调控BiVO4的铁磁性能. 在N2气氛中退火后, BiVO4晶面异质结中氧空位的比例随着{010}/{110}晶面比例的增加而降低, 因为{010}晶面上氧空位的形成能低于{110}晶面. {010}/{110}晶面比例较低的BiVO4晶面异质结的铁磁性能优于{010}/{110}晶面比例较高的BiVO4, 因为前者颗粒尺寸更小、更立体, 其比表面积和界面区域更大, 所以其表面未饱和自旋对总磁矩的贡献更大. {010}/{110}比例较高的BiVO4晶面异质结具有更大的光电流密度和光电催化产氢效率, 源于BiVO4{010}晶面比{110}晶面具有更高的电荷迁移率、更好的吸附特性和更低的能垒. 并且氧空位的引入也提高了BiVO4的制氢效率.

关键词: 铁磁光催化剂, 氧空位, BiVO4晶面异质结, 产氢

In ferromagnetic photocatalysts, most charges have the same spin state, which suppresses photogenerated electron-hole recombination. However, ferromagnetic photocatalysts are rare, and the impact of spin is negligible in nonferromagnetic photocatalysts. In this study, the ferromagnetic properties of BiVO4 are regulated in terms of crystal plane orientation and oxygen vacancy synergism, considering the different formation energies of oxygen vacancies in its {010} and {110} planes. BiVO4 powders with tunable crystal facets are synthesized by using a solvothermal method. The synthesized BiVO4 surface heterojunctions with {010}/{110} crystal plane ratios of 0.17 and 0.93 are referred to as BiVO4-pH=0.5 and BiVO4-pH=1, respectively. The density of oxygen vacancies in BiVO4 is regulated by annealing at 450 ℃ for 2 h in a N2 atmosphere inside a tube furnace. The annealed BiVO4 surface heterojunctions are called BiVO4-pH=0.5-N2 and BiVO4- pH=1-N2. X-ray photoelectron spectroscopy is performed to examine the ratios of the number of surface oxygen vacancies to the number of surface oxygen atoms at the intrinsic sites (OV/OL). The ratios for BiVO4-pH=1, BiVO4-pH=1-N2, BiVO4-pH=0.5, and BiVO4-pH=0.5-N2 are 18.96%, 20.36%, 16.04%, and 21.42%, respectively. Thermogravimetric analysis is performed to determine the concentration of oxygen vacancies because the oxygen vacancies are refilled with oxygen atoms at high temperatures resulting in weight gain. The OV/OL ratios for the entire material are 0.56% and 0.23% for BiVO4-pH=0.5-N2 and BiVO4-pH=1-N2, respectively. The proportion of oxygen vacancies in the BiVO4 surface heterojunctions decreases with increasing {010}/{110} ratio after annealing in the N2 atmosphere. This is because the formation energy of oxygen vacancies in the {010} plane is lower than that in the {110} plane. The ferromagnetic properties of the BiVO4 surface heterojunctions are correlated to the concentration of oxygen vacancies and the ratio of the {010}/{110} crystal planes. The ferromagnetic properties of BiVO4 with a lower {010}/{110} ratio (BiVO4-pH=0.5) are superior to those of BiVO4 with a higher {010}/{110} ratio (BiVO4-pH=1). BiVO4-pH=0.5 has a smaller particle size and is more three-dimensional, indicating a larger specific surface area and interfacial region. The contribution of the surface unsaturated spin to the total magnetic moment in BiVO4-pH=0.5 is higher than that in BiVO4-pH=1. The introduced oxygen vacancies enhance the ferromagnetic properties of BiVO4-pH=0.5 as well as the photoelectrocatalytic H2 production properties of the BiVO4 surface heterojunctions (BiVO4-pH=0.5 and BiVO4-pH=1). The formal quantum efficiency (FQE) used in this study is synonymous with the photonic efficiency calculated from the known spectral distribution of the excitation source and known absorption spectrum of the reaction system. The FQE values of BiVO4-pH=1, BiVO4-pH=1-N2, BiVO4-pH=0.5, and BiVO4-pH=0.5-N2 are 0.0086%, 0.045%, 0.0019%, and 0.032%, respectively. The enhanced photoelectrocatalytic performance can be attributed to the significantly increased visible light absorption capacity, rapid transport of electrons and holes, high photogenerated electron-hole separation efficiency, and improved reduction potential. In particular, BiVO4 with a higher {010}/ {110} ratio exhibits a higher photocurrent density and a greater H2 production efficiency because the {010} facets have higher charge mobility, better water adsorption characteristics, and lower energy barrier compared to the {110} facets.

Key words: ferromagnetic photocatalyst, oxygen vacancy, BiVO4 surface heterojunction, hydrogen production