Enhanced Photoelectrochemical Water Oxidation Performance on BiVO₄ by Coupling of CoMoO₄ as a Hole-Transfer and Conversion Cocatalyst

Abstract

Manipulation of interfacial charge separation and transfer is one of the primary breakthroughs to improve the water oxidation activity and stability of BiVO₄ photoanode. In the present work, a CoMoO₄-coupled BiVO₄ (BiVO₄/CoMoO₄) film was designed and prepared as the photoanode for photoelectrochemical (PEC) water oxidation. Compared with the bare BiVO₄ film, obviously improved PEC water oxidation performance was observed on the BiVO₄/CoMoO₄ film. Specifically, a higher water oxidation photocurrent density of 3.04 mA/cm² at 1.23 V versus RHE was achieved on the BiVO₄/CoMoO₄ photoanode, which is of about 220% improvement over bare BiVO₄ photoanode (1.34 mA/cm² at 1.23 V vs RHE). In addition, the BiVO₄/CoMoO₄ film photoanode was of better stability and faster hole-to-oxygen kinetics for water oxidation, without significant activity attenuation for 6 h of reaction at 0.65 V versus RHE. The enhanced water oxidation performance on the BiVO₄/CoMoO₄ film photoanode can be ascribed to the synergistic effect of the following factors: (i) thermodynamically, the photogenerated holes of BiVO₄ are directionally transferred to CoMoO₄ through their physical coupling interface and valance band potential matching; and (ii) kinetically, the transferred holes induce the formation of Co³⁺-active sites on CoMoO₄ that could synergistically oxidize H₂O to molecular O₂ with stable activity.