Rapid high-temperature hydrothermal post treatment on graphitic carbon nitride for enhanced photocatalytic H₂ evolution

Hydrothermal treatment has been widely employed for material synthesis and modification. In this work, with the help of the homemade microreactor, a rapid high-temperature hydrothermal post treatment (RHTHTPT) process with fast heat transfer and short processing time was elaborately designed for graphitic carbon nitride (g-C₃N₄). Taking advantage of high temperature and short duration time during RHTHTPT process, the RHTHTPT-derived g-C₃N₄ reached up to a high product yield over 80%. The RHTHTPT-derived g-C₃N₄ showed an enhanced photocatalytic H₂-evolution activity about 5.1 times that of pristine g-C₃N₄ under visible-light irradiation (λ > 400 nm). With systematic characterizations and the tracking of gas-liquid-solid products by RHTHTPT, it was found that the RHTHTPT could effectively enlarge the specific surface area to increase the active sites for photocatalytic H₂-evolution reaction, abundant amino groups and the insertion of oxygen-containing functional groups in the surface of g-C₃N₄ could realize efficient carriers separation, both of which gave rise to the improved photocatalytic H₂-evolution performance. This work develops a promising hydrothermal strategy to regulate the in-plane structure of g-C₃N₄ and brings a deeper understanding for the correlation between RHTHTPT-induced structure modification with photocatalytic ability, and therefore further provides some guidelines for directionally designing the special structures of g-C₃N₄ as well as other potential materials by hydrothermal modification.