In situ constructing intramolecular ternary homojunction of carbon nitride for efficient photoinduced molecular oxygen activation and hydrogen evolution

Polymeric semiconductors potentially rich in Frenkel excitons are booming in photocatalysis, but most of them only show moderate performance in hydrogen evolution and molecular oxygen activation due to the sluggish electron-hole pair dissociation and charge transfer dynamics. Herein, a novel design of intramolecular g-C3N4-based ternary homojunction is established via one step KSCN/NH4Cl-assisted ionothermal route. The integrated theoretical calculations and experimental results disclose that such a unique ternary structure not only dramatically expedite intralayer exciton splitting and interface charge transfer but also greatly reduce backward charge recombination through the arrangement of HOMO/LUMO levels and consequent internal electric field. As a result, the optimal sample exhibits remarkable enhancements in oxygen (O-2) reduction to hydroxyl radicals (center dot OH), and water splitting with H-2 evolution rate (3806.5 mu mol h(-1) g(-1)) about 17.8 times higher than that of unmodified melon outperforming most functionalized g-C3N4 and heterojunctions reported thus far. Our study highlights the rational design of chemical structures to modulate the excitonic features and charge-transfer properties of polymeric semiconductors for efficient solar energy utilization.