Photocatalytic Hydrogen Evolution Performance for Hydroxyl-rich Porous Carbon Nitride

Metal-free photocatalyst C₃N₄ has been well investigated, while how to create hydroxyl-rich porous C₃N₄ remains a great challenge. Herein, we report a facile approach to address this issue by developing a novel two-step process:(i) precursor achieved via freeze-drying the mixture of urea, thiourea and NH₄Cl; (ii) subsequent thermal polydensation of the precursor. Systematic sample characterization demonstrated the formation of C₃N₄ featured by unique hydroxyl-rich porous structure with an extended tri-s-triazine unit. When applied as photocatalyst for water splitting under UV-Vis light irradiation, the sample displays a high hydrogen evolution rate of 243.4 μmol·g^-1·h^-1, about 4 times higher than that of C₃N₄ prepared by conventional method. Such a performance enhancement could be due to the porous structure and surface hydroxyl-rich functional groups that promote multiple-times reflection and light absorption, increase the active site numbers, and improve carrier transfer/separation efficiency.