Hydrochloric-acid-induced hydrothermally pretreated ultrathin C₃N₄ nanosheets for efficient photocatalytic H₂ evolution

BACKGROUND: C3N4 nanosheets with a layered structure have attracted significant interest in the field of photocatalysis. However, direct preparation of these nanosheets remains a significant challenge. RESULTS: In this study, highly active C3N4 nanosheets were fabricated via the direct thermal polymerization of melamine supramolecular aggregates obtained using hydrochloric-acid-induced hydrothermal pretreatment. Various methods were adopted to characterize the photocatalytic materials obtained and density functional theory calculations were performed to understand the highly efficient nature of C3N4. The structures and photochemistry of the photocatalytic materials depend on the hydrochloric-acid-induced hydrothermal pretreatment method. It was found that C3N4-180-H nanosheets have numerous (C)(2)N-H that are conducive to photogenerated electron-hole separation. In addition, the C3N4-180-H nanosheets have a large surface area and a short charge-carrier diffusion distance. Furthermore, the C3N4-180-H nanosheets exhibited a longer excitation-state charge-carrier lifetime than bulk C3N4. The as-prepared C3N4-180-H nanosheets with unique structural advantages showed superior photocatalytic H-2 evolution performance (413 mu mol h(-1) g(-1)) compared to that of bulk C3N4 (90.5 mu mol h(-1) g(-1)). CONCLUSION: This study offers a feasible and simple method for synthesizing C3N4 nanosheets and developing an excellent 2D photocatalyst for superior solar-to-H-2 production. (c) 2023 Society of Chemical Industry (SCI).