Using VO2 as a hole storage layer to improve PEC water splitting performance of BiVO4 photoanode

Because of its advantageous band gap and band edge, BiVO4 is thought to be a viable photoanode for photoelectrochemical (PEC) water splitting. However, its photoelectrochemical water splitting capability is primarily restricted by photogenerated carrier recombination. In order to address this issue, a hole storage layer (HSL) VO2 was deposited onto a W-doped BiVO4 photoanode through photoelectric deposition in this study. During PEC water oxidation, the ultrathin VO2 layer's reversible V4+ species can regulate the hole-storage process, improving hole extraction capacity and reducing charge recombination. As expected, under AM 1.5 G illumination, the optimized W–BiVO4/VO2/Co-Pi photoanode exhibits a photocurrent density of 5.6 mA/cm2 at 1.23 V vs. RHE with an onset potential of 0.28 V. This value exceeds pure BiVO4 (1.1 mA/cm2) by around 409%. Based on results from experiments, the charge transfer efficiency of the W–BiVO4/VO2/Co-Pi photoanode reaches 96.3%, showing excellent PEC water splitting performance.