Green light all the way: Triple modification synergistic modification effect to enhance the photoelectrochemical water oxidation performance of BiVO photoanode.

The recombination of photogenerated electron-hole pairs of the photoanode seriously impairs the application of bismuth vanadate (BiVO) in photoelectrochemical water splitting. To address this issue, we prepared a Yb:BiVO/CoO/FeOOH composite photoanode by employing drop-casting and soaking methods to attach CoO/FeOOH cocatalysts to the surface of ytterbium-doped BiVO. The prepared Yb:BiVO/CoO/FeOOH photoanode demonstrates a high photocurrent density of 4.89 mA cm at 1.23 V versus the reversible hydrogen electrode (RHE), which is 5.1 times that of bare BiVO (0.95 mA cm). Detailed characterization and testing demonstrated that Yb doping narrows the band gap and significantly enhances the carrier density. Furthermore, CoO serves as a hole transfer layer to expedite hole migration and diminish recombination, while FeOOH offers additional active sites and minimizes surface trap states, thus boosting stability. The synergistic effects of Yb doping and CoO/FeOOH cocatalyst significantly improved the reaction kinetics and overall performance of PEC water oxidation. This work provides a strategy for designing efficient photoanodes for PEC water oxidation.