Integrating P-Doped Carbon Nitride Dots as Active Sites on P/Mo Co-Doped BiVO₄ Photoanodes Promotes H₂O₂ Production

The indirect anthraquinone method is currently used to produce H₂O₂, but it leads to high energy consumption and a large amount of chemical waste. Alternatively, water oxidation reactions offer a potential green approach for H₂O₂ production, although it is constrained by low selectivity. Herein, the functional photoanodes are rationally designed for H₂O₂ production via photocatalytic water oxidation. Specifically, P/Mo co-doped BiVO₄ films are achieved on a conductive glass to serve as the photocatalytic layer, which is coated with an ultrathin amorphous TiO₂ film to achieve good stability. Importantly, metal-free P-doped polymeric carbon nitride dots are deposited on the photoanode, acting as the reaction centres. This innovative approach moves away from the traditional reliance on inorganic materials as co-catalysts in order to suppress the thermodynamically favoured O₂ evolution, which, in turn, significantly enhances the selectivity, efficiency and stability of H₂O₂ production. Consequently, an optimal selectivity of ≈64% for H₂O₂ production is achieved at an applied voltage bias of 1.7 V versus RHE in a 1.0 m KHCO₃ solution, achieving a yield of ≈34.2 µmol hr^-1 cm^-2. This research offers a novel strategy for developing photocatalytic films with optimised co-catalysts for a photoanode in photocatalytic H₂O₂ synthesis.