The direct Z-scheme character and roles of S vacancy in BiOCl/Bi2S3-(001) heterostructures for superior photocatalytic activity: a hybrid density functional investigation

Abstract

Given some current speculations and controversies regarding the type of BiOCl/Bi₂S₃-(001) heterostructure in experiments, it is of great importance to clarify these controversies and further explain the relevant experimental results. In this work, based on first-principles hybrid density functional calculations, it is verified that the BiOCl/Bi₂S₃-(001) heterostructure is a direct Z-scheme photocatalyst with high photo-generated carrier separation efficiency and strong redox ability that can react with O₂ and OH⁻ to produce photocatalytic active species of superoxide ions (˙O₂⁻) and hydroxyl radicals (˙OH), respectively. This is consistent with the experimental findings and explains the excellent photocatalytic performance of the BiOCl/Bi₂S₃-(001) heterostructure in experiments. Besides, excitingly, it is found that the optical absorption, built-in electric field intensity, interlayer recombination probability, hydrogen evolution reaction ability, and the difference in electron–hole mobility are further enhanced via S vacancy introduction in BiOCl/Bi₂S₃-(001). Therefore, the significant roles of S vacancy in further improving the photocatalytic properties of the BiOCl/Bi₂S₃-(001) heterostructure are profoundly revealed. This work can provide valuable theoretical insights for designing the superior direct Z-scheme BiOCl/V_S-Bi₂S₃-(001) heterostructure with promising photocatalytic properties.