From sole protection to synergistic water oxidation: A Mo-doped functionalized Nb 2 O 5 layer on BiVO 4 photoanodes

Abstract BiVO4 photoanodes are promising for solar-driven water oxidation, but their performance is often limited by inefficient interfacial hole utilization and inadequate operational stability. Herein, via Mo modification, a conventional passive Nb2O5 protective layer on FeOOH/BiVO4 is converted into a functional interfacial layer, simultaneously enhancing photoelectrochemical activity and stability. The resulting Mo:Nb2O5/FeOOH/BiVO4 photoanode delivers a photocurrent density of 6.27 mA/cm2 at 1.23 V vs. RHE under AM 1.5G illumination and maintains stable operation for over 100 h at 0.7 V. Electrochemical analyses reveal markedly suppressed charge recombination and improved interfacial hole utilization. Combined Kelvin probe force microscopy, in situ light-assisted X-ray photoelectron spectroscopy, surface photovoltage measurement and density functional theory calculation demonstrate that Mo incorporation modulates the light-induced interfacial potential redistribution, reconstructs near-Fermi-level electronic states, and promotes a more favorable oxygen evolution reaction pathway. These findings provide an effective strategy for constructing high-performance BiVO4 photoelectrodes by functionalizing a passive protective layer.