Ultrathin porous carbon nitride nanosheets with well-tuned band structures via carbon vacancies and oxygen doping for significantly boosting H2 production

Significant improving g-C 3 N 4 ’s photocatalytic efficiency still remains a great challenge. In this work, we synthesized ultrathin and porous 2D g-C 3 N 4 nanosheets with a controllable concentration of carbon vacancies and oxygen doping. Water vapor opens the heptazine units, introduces carbon vacancies, and acts as an oxygen source for oxygen doping under high temperatures. The synergistic effect of controllable carbon vacancies and oxygen doping can continuously regulate band structures and significantly improves the separation efficiency of photoexcited charges. As a result, the prepared g-C 3 N 4 with vigoroso reduction potential exhibits a very high photocatalytic H 2 evolution rate of 2.414 mmol g −1 h −1 under visible light and 7.414 mmol g −1 h −1 under ultraviolet-visible light, respectively, which outperforms the majority of the previously reported g-C 3 N 4 with well-tuned band structure. This work offers a new design idea for highly active g-C 3 N 4 -based photocatalysts with a well-tuned band structure. A step-by-step synergistic etching/stripping strategy is developed for preparing ultrathin and porous 2D g-C 3 N 4 nanosheets with controllable carbon vacancies and oxygen doping with a great potential in photocatalysis. • Ultra-thin and porous 2D g-C 3 N 4 nanosheets with controllable carbon vacancies and oxygen doping are prepared. • Water vapor opens the heptazine units, introduces carbon vacancies, and acts as oxygen sources for oxygen doping under high temperatures. • Synergistic effect of controllable carbon vacancies and oxygen doping can continuously regulate band structures. • Rapid separation of photoexcited charges and up-shift of conduction band boost photocatalytic performance..