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 the 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 the 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 RHE, corresponding to the incident photon-to-current conversion efficiency of 63% at 430 nm. This work provided an effective strategy to design photothermal material assisted photoelectrode for efficient water splitting.

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BACKGROUND: Semiconductor-based photoelectrochemical (PEC) water splitting represents one attractive route to generate clean hydrogen. Cu 2 ZnSnS 4 (CZTS) is considered a promising photoelectric material for PEC water splitting due to its high absorption coefficient, small bandgap, nontoxicity, and earth-abundant elements. Only a few critical parameters limit the performance of CZTS nanocrystal films. Of those, heat treatment is essential for producing high-performance films.RESULTS: In this work, CZTS nanocrystals were produced by a facile method and applied in making CZTS films for PEC water reduction. Therefore, the influences of heat treatment parameters on the performance of films were investigated in the lowtemperature heat treatment range. The surfactant polyvinylpyrrolidone (PVP) in the films could not be completely decomposed at low heat treatment temperatures, leading to film resistance that was harmful to the PEC process. Meanwhile, SnS x impurities would arise at temperatures over 400 °C, thus reducing the PEC performance.CONCLUSION: The best activity for PEC water reduction was obtained at 385 °C for 10 min. Furthermore, the PEC performance of CZTS films generated by fast heating (10 °C s −1 ) was superior to that of films generated by slow heating (10 °C min −1 ) due to the inhibition from the development of SnS x impurities.