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.