Water-assisted formation of amine-bridged carbon nitride: A structural insight into the photocatalytic performance for H2 evolution under visible light

Carbon nitride (C3N4) exhibits significant potential as a metal-free photocatalyst for H2 production using visible light. While the C3N4 network consists of tri-s-triazine building units linked by H bonds, it is still controversial how the H bonds affect the photocatalytic performance. In this study, we present a water-assisted method for production of polymeric carbon nitride to control intraplanar structures associated with H bonds and amine bridges. The C3N4 samples produced with a thermal treatment using water and humidified air gas (CN-H) exhibit excellent photocatalytic activities for the hydrogen evolution reaction. From structural and photophysical characterizations, it is found that CN-H samples contain fewer H bonds and more amine bridging groups as well as possess larger domains than C3N4 samples produced without using water (CN-A). These structural changes induced by the water treatment lead to efficient intraplanar migration of photoexcited charge carriers and thus are responsible for the enhanced photocatalytic performances.