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

Abstract

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 V_RHE), 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.