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

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.