Achieving photocatalytic water reduction and oxidation over narrow band gap FeVO₄

The exploration of novel oxide photocatalysts with narrow bandgaps is highly desirable for efficient photocatalytic water splitting. However, it is rather challenging since with decreasing the bandgap, severe charge recombination generally accompanies for the photocatalysts. To address those issues, the present work demonstrates that the triclinic FeVO₄ with an absorption edge of 575 nm can be synthesized and applied for visible-light-driven photocatalytic water reduction and oxidation for the first time. Based on it, the Cr doping strategy is implemented on the FeVO₄ photocatalyst to further promote the charge separation as well as the photocatalytic water splitting performance, whose apparent quantum efficiency (AQE) of 0.26% at 420 nm (± 15 nm) can be achieved for an O₂ evolution reaction. Detailed analysis shows that an impurity level below the conduction band minimum originated from the Cr 3d orbital is formed after Cr doping, facilitating the prolonged absorption edge and the enhanced charge separation. This work inaugurates the application field of the narrow bandgap particulate FeVO₄ photocatalyst in photocatalytic water splitting, and validates the charge separation can be promoted by Cr doping, both of which are promising to be further developed for efficient solar energy conversion.