Carbon-vacancy engineering approach to g-C3N4 for selective 5-hydroxymethylfurfural oxidation coupled with H2O2 production

Abstract

Photocatalytic H₂O₂ production and selective oxidation of 5-hydroxymethylfurfural (HMF) occur in synergy, which improves the utilization of photogenerated carriers. In this paper, g-C₃N₄ (CN) under defect engineering was used in the photocatalytic production of H₂O₂ and HMF oxidation. It was found that H₂O₂ productivity has the order of Cv-CN (283.9 μmol g⁻¹ h⁻¹) > Nv-CN (241.4 μmol g⁻¹ h⁻¹) > CN (154.0 μmol g⁻¹ h⁻¹), the DFF yield correlates positively with the above order, and that of Cv-CN reached as high as 50.7 μmol L⁻¹. The yield of H₂O₂ and 2,5-dicarbonylfuran (DFF) was increased by 1.7 times and 6.3 times compared with the original CN, respectively. The lowest PL intensity and longest fluorescence lifetime indicate higher charge separation efficiency of Cv-CN. DFT calculations show that the electron–hole separation on Cv-CN is better compared to CN and the formation of H₂O₂ on Cv-CN has a lower energy barrier, which will be beneficial for the adsorption/activation of O₂. Selective oxidation of HMF to DFF using noble metal-free catalysts under mild reaction conditions combined with H₂O₂ production can both reduce the electron/hole complexation rate and increase the added value of the reaction. This designed bifunctional photocatalytic system may be more feasible and practical from a sustainable and green development perspective. This work also thus provides a new method/material for photocatalytic production of H₂O₂ and selective oxidation of HMF.