Comprehensive Study of the Growth Mechanism and Photoelectrochemical Activity of a BiVO₄/Bi₂S₃ Nanowire Composite

A BiVO₄/Bi₂S₃ composite comprising Bi₂S₃ nanowires on top of a BiVO₄ film was prepared via hydrothermal reaction. Because additional Bi³⁺ ions were not delivered during the reaction, BiVO₄ served as the Bi³⁺ ion source for the development of Bi₂S₃. A detailed growth mechanism of the nanowire was elucidated by an analysis of the concentration gradient of Bi³⁺ and S^2– ions during the reaction. The in situ growth was followed by the etching of BiVO₄ to Bi³⁺ and VO₄^3– ions and regrowth to Bi₂S₃, which resulted in the rapid evolution of nanowires on the BiVO₄ substrate. The fabricated BiVO₄/Bi₂S₃NW composite exhibited an improved photoelectrochemical activity compared to other Bi₂S₃ samples. The improved efficiency was mainly attributed to both improved charge separation and effective adhesion obtained by the in situ growth.