Construction Of CdX（X=Se，S）/BiVO₄ Heterostructure And Hydrogen Production Performance

In recent years,the fossil energy crisis and its combustion have brought a series of environmental pollution problems,prompting scientists to develop renewable clean energy.As a new energy source with many advantages,hydrogen energy has received extensive attention from researchers.The production of hydrogen by solar energy splitting water is one of the most advantageous ways to prepare hydrogen.Through these years of research,researchers have developed many semiconductor photocatalysts and corresponding hydrogen production systems by splitting water,and developed various strategies to improve the conversion efficiency of solar energy to hydrogen energy.However,the single-component photocatalysts Cd Se,Cd S and Bi VO₄ have low photocatalytic hydrogen production efficiency due to serious photogenerated electron-hole recombination,poor photostability,and poor electron conductivity.The construction of a heterojunction photocatalyst to improve the performance of hydrogen production has great potential.In this paper,the Type-II Bi VO₄/Cd Se and Z-scheme Cd Se/Bi VO₄ heterojunction thin film electrodes were constructed respectively,and S-scheme Bi VO₄/Cd S and Cd S/Bi VO₄heterojunction thin film electrodes were constructed to increase the separation and transmission efficiency of Bi VO₄ carrier,and the transfer of holes in the valence band of Cd Se and Cd S,can achieve the purpose of resisting photocorrosion,thereby improving hydrogen production activity of single component photocatalysts.（1）The Cd Se-Bi VO₄ heterojunction film photoelectrodes were prepared by electrochemical deposition and successive ionic layer adsorption and reaction（s-SILAR）method with FTO as the base.With the help of surface photovoltage technology,the formation process of the built-in electric field and the carrier transport mechanism of two heterojunction film electrodes are explored,Cd Se/Bi VO₄ and Bi VO₄/Cd Se form Z-scheme and Type-II heterojunctions,respectively,and the reasons for the formation of different heterojunctions were analyzed through XPS and DFT analysis.The photocatalysis and photoelectrocatalysis hydrogen production properties of the film electrodes were tested,the Z-scheme Cd Se/Bi VO₄ heterojunction can retain the strong reduction ability of Cd Se electrons and improve the efficiency of carrier separation,which show the best performance of photocatalysis hydrogen production and its photocatalysis hydrogen production rate can reach 2.59μmol·cm^-2·h^-1;while for the Bi VO₄/Cd Se electrode,the construction of Type-II heterostructure can improve the carrier separation efficiency and show the best photoelectrocatalysis hydrogen production performance,and the hydrogen production rate can reach 8.65μmol·cm^-2·h^-1.（2）The Cd S-Bi VO₄ heterojunction film photoelectrodes were prepared by chemical bath deposition and successive ionic layer adsorption and reaction（s-SILAR）method with FTO as the base.With the help of surface photovoltage technology,the formation process of the built-in electric field and the carrier transport mechanism of heterojunction in the two film electrodes are explored,S-scheme heterojunction formed between Cd S and Bi VO₄.The photocatalysis and photoelectrocatalysis hydrogen production properties of the film electrodes were tested,because the charge transfer mechanism affects the way of hydrogen production,Bi VO₄/Cd S shows the best photocatalysis hydrogen production performance,and its hydrogen production rate can reach 0.18μmol·cm^-2·h^-1,while Cd S/Bi VO₄ shows the best photoelectrocatalysis hydrogen production performance,and its hydrogen production rate can reach 11.39μmol·cm^-2·h^-1.