Improved Performance of BiVO₄ via Surface-Deposited Magnetic CuFe₂O₄ for Phenol Oxidation and O₂ Reduction and...

Monoclinic BiVO₄ (BiV) is a good photoanode for water oxidation but a poor photocatalyst for organic oxidation because of slow O₂ reduction. In this work, a well-crystallized BiV microdecahedron (1-2 μm) has been deposited with a poorly crystallized cubic CuFe₂O₄ (CF) nanosphere (100 nm). For phenol oxidation and O₂ reduction to H₂O₂ in aqueous suspension under visible light, 1 wt % CF/BiV was more active than BiV by approximately factors of 14 and 7, respectively, while CF was almost not active. A (photo)electrochemical measurement showed that CF/BiV was more active than BiV not only for phenol and water oxidation under visible light but also for O₂ reduction and water oxidation in the dark. Moreover, as compared to BiV, CF/BiV was more efficient in the charge transfer to a solution species but less efficient either in the light-on electron generation or in the light-off electron disappearance. Based on the solid band edge potentials measured by ultraviolet photoelectron spectroscopy, a possible Z scheme mechanism is proposed involving charge recombination at the CF/BiV interfaces followed by the increased O₂ reduction on CF and the increased phenol oxidation on BiV.