Tuning surface electronegativity of BiVO4 photoanodes toward high-performance water splitting

Photoelectrochemical (PEC) water splitting is a promising technique for converting solar energy into hydrogen fuels, while its practical applications are mainly restricted by the relatively low photo-conversion efficiencies. Herein, we demonstrated a simple surface fluorination process for drastically promoting the PEC water oxidation activity of BiVO4 photoanodes, achieving a remarkable photocurrent density of 3.2 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) under AM 1.5 G illumination, one of the highest values of BiVO4 electrodes without cocatalysts. After in-situ formation of CoF2 cocatalysts, the photocurrent density could be further increased up to 5.1 mA cm−2 (1.23 VRHE), accompanying by a remarkably negative shift of onset-potential (270 mV). Systematic studies clearly reveal that tuning surface electronegativity of BiVO4 photoanodes could drastically promote the charge separation efficiencies of both surface and bulk up to nearly 100%. This work may provide a facile but effective approach for constructing the highly efficient BiVO4 photoanodes for solar water splitting.