BiVO Film Coupling with CoAlO Nanoparticles for Photoelectrochemical Water Splitting Utilizing Broad Solar Spectrum through p-n Heterojunction, Photothermal, and Cocatalytic Synergism.

Water oxidation is an endothermic and kinetics-sluggish reaction; the research of photoanodes with photothermal and cocatalytic properties is of great significance. Herein, BiVO/CoAlO film photoanodes were studied for solar water splitting through coupling spinel p-type CoAlO nanoparticles on n-type BiVO films. Compared to the BiVO photoanode, better performance was observed on the BiVO/CoAlO photoanode during water oxidation. A photocurrent of 3.47 mA/cm was produced on the BiVO/CoAlO photoanode at 1.23 V vs RHE, which is two-fold to the BiVO photoanode (1.70 mA/cm). Additionally, the BiVO/CoAlO photoanodes showed an acceptable stability for water oxidation. The BiVO/CoAlO photoanode being of higher water oxidation performance could be attributed to the presence of p-n heterojunction, cocatalytic, and photothermal effects. In specific, under the excitation of λ < 520 nm light, the holes produced in/on BiVO can be transferred to CoAlO owing to the p-n heterojunctions of BiVO/CoAlO. Meanwhile, the temperature on the BiVO/CoAlO photoanode rises quickly up to ∼53 °C under AM 1.5 G irradiation due to the photothermal property of CoAlO through capturing the 520 < λ < 720 nm light. The temperature rising on the BiVO/CoAlO photoanode improves the cocatalytic activity of CoAlO and modifies the wettability of BiVO/CoAlO for effective water oxidation.