Boosting Photoelectrochemical Performance of BiVO₄ through Photoassisted Self-Reduction

The photoelectrochemical water splitting of monoclinic bismuth vanadate (BiVO4) suffers from sluggish charge mobility as well as substantial charge recombination losses. Here, we treated the BiVO4 by using a photoassisted self-reduction method based on the fact that the self-reduction potential of BiVO4 is more positive than its conduction band. The BiVO4 photoanode subjected to this treatment has a more negative onset potential and higher photovoltage compared with bare BiVO4. Moreover, its charge carrier density and mobility are increased and accelerated compared to bare BiVO4. As a result, the charge separation efficiency reaches to approximate 94% at 1.23 V vs the reversible hydrogen electrode (RHE), and the photocurrent densities are 3.18 and 5.84 mA/cm2 (at 1.23 V vs RHE) in the absence and presence of the sacrificial agent, respectively. In particular, the reduced BiVO4 with electrocatalysts (FeOOH/NiOOH) achieves a photocurrent of 5.06 mA/cm2 at 1.23 V vs RHE, which is 2.54 times higher than that of the bare BiVO4. This approach provides a new strategy for designing a semiconductor-based photoanode with superior performance for photoelectrochemical water splitting.