Copolymerization of Poly (Triazine Imide) Single Crystal Nanoplates with Enhanced Charge Transfer for Efficient Photocatalytic Overall Water Splitting

Solar-driven photocatalytic overall water splitting represents a sustainable strategy to produce green hydrogen using metal-free polymeric carbon nitride. However, conventional thermal polymerization with a single precursor for the synthesis of poly (triazine imide) faces challenges such as slow deamination rates and mass transfer, resulting in the formation of undesired structural defects, which usually serve as charge recombination sites and decrease the photocatalytic performance. Herein, highly crystalline poly (triazine imide) by thermal copolymerization of binary precursors of melamine and cyanuric acid in the presence of molten salts is reported. The results reveal that melamine and cyanuric acid easily generate melam (intermediates of carbon nitride) and subsequently facilitate the polycondensation process. Solid characterizations revealed that crystalline poly (triazine imide) nanoplates with extended pi-conjugation degrees and reduced intensity of structural defects would be obtained, which largely promotes separation and migration of photogenerated carriers, and inhibits the undesirable charge recombination at the defect sites. Accordingly, after in situ photo-deposition of CoOx and Pt/Cr2O3 as O2 and H2 evolution co-catalysts, respectively, the optimized crystalline poly (triazine imide) nanoplates achieve an excellent solar-to-hydrogen conversion of 0.30% under simulated sunlight irradiation.