Onion-like carbon with controllable carbon atom hybridization embedded in BiVO4 photoanode for enhanced photoelectrochemical water splitting

BiVO4 with a suitable energy band structure is one of the most promising substrates for photochemical water spitting, but a significance limitation is its severe recombination of photogenerated electron-hole pairs in the bulk. Herein, we present a strategy of incorporating an onion-like carbon (OLC) into bulk BiVO4 matrix to enhance its carrier separation. The OLC, with controlled sp2/sp3-carbon ratio, can facilitate the bulk charge separation and UV–vis light absorption of BiVO4. The carrier separation enhancement in BiVO4 is highly dependent on the sp2/sp3 ratio of OLC, which falls within the range of 3 % to 89 %. The BiVO4/OLC photoanode embedded by OLC with sp2-carbon content of 40 % exhibits the champion photocurrent density of 4.8 mA cm−2 (1.23 VRHE), compared to the pristine BiVO4 of 2.84 mA cm−2. This work not only demonstrates a strategy for enhancing the photocatalytic carrier separation of BiVO4 photoanode by incorporating OLC, but it also provides a comprehensive understanding of the function mechanism of carbon-based materials in photocatalysts.