Enhanced photocatalytic activity of Z-scheme BiVO4 heterophase junction via giant built-in electric field

Abstract

Built-in electric field (IEF) can improve photocatalytic efficiency by promoting charge separation and transfer. Herein, a Z-scheme BiVO₄ heterophase junction with giant IEF was successfully constructed. By changing the pH value of the precursor solution, the ratio of monoclinic octahedral BiVO₄ (m-BVO) to tetragonal microsphere BiVO₄ (t-BVO) is regulated to form a heterophase junction (mt-BVO), so as to regulate the IEF intensity. When pH = 0.5, a large number of pores were formed at the interface of the two forms in mt-BVO-35%m, so it has a larger specific surface area. mt-BVO-35%m has optimal photocatalytic tetracycline degradation activity. Under visible light irradiation, its reaction rate constant k is shown to be 3 times higher than that of pure m-BVO, and the TOC removal rate has increased from 12 % to 36 %. Through characterization, it can be proved that the IEF strength of mt-BVO-35%m is 11.86 times that of m-BVO. The significantly improved activity is mainly attributed to the presence of a giant IEF between m-BVO and t-BVO. The IEF drives the photogenerated electrons to transfer from the CB of t-BiVO₄ to the VB of m-BiVO₄, which greatly enhances the separation and transfer of photogenerated charge carriers. Moreover, a mechanism of Z-scheme charges transfer pathway in the mt-BVO-35%m heterophase junction was also revealed.