An Electrochemically Treated BiVO4 Photoanode for Efficient Photoelectrochemical Water Splitting

BiVO4 films with (040) facet grown vertically on fluorine doped SnO2 (FTO) glass substrates are prepared by a seed‐assisted hydrothermal method. A simple electrochemical treatment process drastically enhances the photocatalytic activity of BiVO4, exhibiting a remarkable photocurrent density of 2.5 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) under AM 1.5 G illumination, which is approximately 10‐fold higher than that of the pristine photoanode. Loading cobalt borate (CoBi) as cocatalyst, the photocurrent density of the BiVO4 photoanode can be further improved to 3.2 mA cm−2, delivering an applied bias photon‐to‐current efficiency (ABPE) of 1.1 %. Systematic studies reveal that crystal facet orientation also synergistically boosts both charge separation and transfer efficiencies, resulting in remarkably enhanced photocurrent densities. These findings provide a facile and effective approach for the development of efficient photoelectrodes for photoelectrochemical water splitting. Partial reduction of Bi3+ and V5+ using a facile electrochemical treatment effectively improves the bulk and surface charge separation of crystal‐facet‐engineered BiVO4 films, resulting in 10‐fold enhanced photocurrent densities. The discovery of a synergistic effect of electrochemical treatment and crystal facet engineering boosting the PEC performance will open up new opportunities for efficient water splitting.