Controllable Synthesis Heterojunction of g-C3N4 and BiVO4 to Enhance the Photocatalytic Oxygen Evolution Activity

Heterojunctions formed between semiconductors have been confirmed to efficiently enhance the separation of photogenerated carriers, thereby boosting the photocatalytic activity. However, achieving controllable synthesis of heterojunctions remains a challenge. In this study, g-C3N4 (CN) was positively charged by carefully adjusting the pH of the solution. Subsequently, it was precisely located on the (010) crystal facet of decahedral BiVO4 (BVO) under light irradiation, where photogenerated negative electrons accumulate on the (010) facet of BVO. This process results in the construction of a composite with a heterojunction between CN and the (010) facet of BVO. The optimal photocatalytic oxygen production activity of this composite reaches 2966.9 μmol/g/h, a remarkable 3.3 times better than that of BVO alone. This result shows that the heterojunction can significantly improve the oxygen production activity of the composite photocatalyst. By a combination of the Kubelka–Munk function, Mott–Schottky, and theoretical calculations, we found that the migration of photogenerated electrons from BVO to CN matches well with the S-scheme mechanism. This work provides valuable suggestions and guidance for the precise synthesis of heterojunction photocatalyst and is looking forward to being applied to other materials related to environmental and energy research.