Optimization of the Photo‐Electrochemical Performance of Mo‐Doped BiVO₄ Photoanode by Controlling the Metal–Oxygen Bond State on (020) Facet

Abstract

Oxygen vacancy on semiconductor has been usually considered as donor contributor which can improve the charge transfer capacity of the photoanode. However, oxygen vacancy has also been found to perform as recombination center for the photogenerated charges. Herein, electrochemical reduction method is employed to treat the surface of Mo‐doped BiVO 4 (BiMoVO) photoanode. Experimental data indicate that when the reduction potential is located at −0.8 V (vs Ag/AgCl), quasioxygen vacancy is formed on the (020) facet (only BiO bonds crack), the electron mobility and photo‐electrochemical (PEC) current density of the BiMoVO photoanode are increased dramatically. However, with the reduction potential increasing to −1.2 V, oxygen vacancy is formed on the surface of (020) facet (both BiO and VO bonds crack simultaneously), the PEC current density is decreased obviously. Further density functional theory calculation data point out that a moderate level of reduction is a key factor for the adjustment of photoanode performance. Thus, these results demonstrate first that oxygen vacancy actually is not the positive factor to improve the PEC performance of a BiVO 4 photoelectrode, but the quasioxygen vacancy forming on the surface of the active facet is.