Polypyrrole modification on BiVO₄ for photothermal-assisted photoelectrochemical water oxidation

The bismuth vanadate (BiVO₄) photoanode receives extensive attention in photoelectrochemical (PEC) water splitting. However, the high charge recombination rate, low electronic conductivity, and sluggish electrode kinetics have inhibited the PEC performance. Increasing the reaction temperature for water oxidation is an effective way to enhance the carrier kinetics of BiVO₄. Herein, a polypyrrole (PPy) layer was coated on the BiVO₄ film. The PPy layer could harvest the near-infrared light to elevate the temperature of the BiVO₄ photoelectrode and further improve charge separation and injection efficiencies. In addition, the conductive polymer PPy layer acted as an effective charge transfer channel to facilitate photogenerated holes moving from BiVO₄ to the electrode/electrolyte interface. Therefore, PPy modification led to a significantly improved water oxidation property. After loading the cobalt-phosphate co-catalyst, the photocurrent density reached 3.64 mA cm^-2 at 1.23 V vs the reversible hydrogen electrode, corresponding to an incident photon-to-current conversion efficiency of 63% at 430 nm. This work provided an effective strategy for designing a photothermal material assisted photoelectrode for efficient water splitting.