Chemical reduction-induced surface oxygen vacancies of BiVO4 photoanodes with enhanced photoelectrochemical performance

Abstract

Bismuth vanadate (BiVO₄) is one of the highly promising photoanodes for photoelectrochemical (PEC) water splitting but suffers from severe carrier recombination and undesirable charge transfer at the semiconductor–electrolyte interface. Herein, we employ an effective surface-engineered sulfite treatment to improve the PEC performance of BiVO₄ without illumination. This post-synthetic treatment on BiVO₄ photoanodes can substantially enhance the interfacial charge transfer efficiency because of decreased charge carrier recombination arising from both surface oxygen vacancies (O_vac) and surface disordered layers. The as-prepared BiVO₄ exhibits a photocurrent density of 2.2 mA cm⁻² at 1.23 V vs. the reversible hydrogen electrode (RHE) under 1-sun illumination, which is 1.7-times higher than that of pristine BiVO₄. By coating the amorphous FeOOH cocatalyst, the photocurrent density can be further improved to 2.8 mA cm⁻². We demonstrate that the chemical reaction employing a reducing agent with a mild reduction activity can controllably alter the surface states of BiVO₄ photoanodes, providing a facile, efficient, and low-cost strategy to achieve high-performance photoelectrodes.