Ultrathin g-C3N4 as a hole extraction layer to boost sunlight-driven water oxidation of BiVO4-Based photoanode

Abstract Graphitic-phase carbon nitride (g-C3N4) for water oxidation are rarely reported. Herein, ultrathin g-C3N4 insert between OEC (NiOOH, FeOOH, CoPi and CoOOH) and BiVO4 photoanode can enhance the photoelectrochemical performance of the optimized OEC/BiVO4 system. Ultrathin g-C3N4 layers can effectively optimize photo-holes migration routes on the BiVO4 -based photoanode/liquid interface to enforce directional holes extraction and transfer, thus prolonging holes trapping lifetime. More specifically, the effect of thickness on holes extraction is revealed and the thickness of ultrathin g-C3N4 layers is optimized. A photocurrent density of 4.20 mA cm −2 (1.23 V vs. RHE) is achieved by CoOOH/g-C3N4/BiVO4, which is 4.29 times higher than pure BiVO4. The applied bias photon-to-current efficiency achieves 1.65% at 0.62 V vs. RHE, which is 10.31 times compared with pristine BiVO4 (0.16%, 0.89 V vs. RHE). This work shed light on design and fabrication of the BiVO4 -based photoanode interface for application in solar light to fuel conversion.