The effect of Fe(iii) ions on oxygen-vacancy-rich BiVO4 on the photocatalytic oxygen evolution reaction

Abstract

Achieving efficient separation and transfer of the photogenerated carriers is significant in improving photocatalytic water oxidation activity over BiVO₄. This is strongly related to the particle structure and surface chemistry. Here, a BiVO₄ photocatalyst is synthesized by a co-precipitation method, in which urea is used as a pH modifier and bubble template growth agent. The synthesized BiVO₄ particles show abundant oxygen vacancies and a higher {110} to {010} facet ratio than the case without a urea agent. The optimized BiVO₄ samples exhibit very high catalytic activity, with the oxygen evolution rates of 680 μmol h⁻¹ and 176 μmol h⁻¹ with the sacrificial agents AgNO₃ and Fe(NO₃)₃, respectively, corresponding to the apparent quantum efficiency (AQE) of 77.8% and 19.6% under 420 nm light irradiation. Interestingly, both results exceeded the theoretical oxygen evolution values which calculated from the reduction number of metal cations (Fe³⁺ → Fe²⁺, Ag⁺ → Ag). Based on a series of comparative experiments, we speculated that a new reaction might occur on the surface of BiVO₄ in the solution during the photocatalytic oxygen evolution. It is expected that the proposed strategy and reaction mechanism could be extended to other photocatalysts' designs and applications.