Rapid Formation of a Disordered Layer on Monoclinic BiVO₄: Co-Catalyst-Free Photoelectrochemical Solar Water Splitting

A surface disordered layer is a plausible approach to improve the photoelectrochemical performance of TiO₂. However, the formation of a crystalline disordered layer in BiVO₄ and its effectiveness towards photoelectrochemical water splitting has remained a big challenge. Here, we report a rapid solution process (within 5 s) that is able to form a disordered layer of a few nanometers thick on the surface of BiVO₄ nanoparticles using a specific solution with a controllable reducing power. The disordered layer on BiVO₄ alleviates charge recombination at the electrode–electrolyte interface and reduces the onset potential greatly, which in turn results in a photocurrent density of approximately 2.3 mA cm⁻² at 1.23 V versus the reversible hydrogen electrode (RHE). This value is 2.1 times higher than that of bare BiVO₄. The enhanced photoactivity is attributed to the increased charge separation and transfer efficiencies, which resolve the intrinsic drawbacks of bare BiVO₄ such as the short hole diffusion length of around 100 nm and poor surface oxygen evolution reactivity.