Preparation of a BiVO₄ nanoporous photoanode based on peroxovanadate reduction and conversion for efficient photoelectrochemical performance

A unique, controllable and facile method based on peroxovanadate reduction and conversion to prepare BiVO₄ nanoporous films is presented. In this method, a slow and controllable reduction of peroxovanadate with ethanol was used, which was the crucial step to ensure the uniform deposition of V₂O₅·xH₂O on an F-doped tin oxide substrate, and subsequently the annealed V₂O₅·xH₂O film was converted to a BiVO₄ film by a simple impregnation method with Bi³⁺ under the oriented effect of polyethylene glycol. The converted BiVO₄ film possessed a single monoclinic scheelite structure and exhibited an optimal water splitting photocurrent density of 1.10 mA cm^-2 at 1.23 V vs. RHE in 0.1 M KH₂PO₄ (pH 7) under AM 1.5G illumination with an incident photon-to-current conversion efficiency of ∼22.4% at 400 nm using an annealed V₂O₅·xH₂O film deposited for 3 hours. The BiVO₄ film also showed excellent water splitting performance and degradation efficiency in the PEC degradation of methylene blue and tetracycline hydrochloride with a rate constant of 0.63 h^-1 and 0.21 h^-1, respectively.