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.