Preparation of graphitic carbon nitride with large specific surface area and outstanding N2 photofixation ability via a dissolve-regrowth process

Nitrogen fixation is the second most important chemical process in nature next to photosynthesis. Here, we report a convenient dissolve-regrowth method for synthesizing graphitic carbon nitride (g-C₃N₄) with a large surface area and nitrogen vacancies by HCl treatment. XRD, N₂adsorption, SEM, TEM, UV–Vis spectroscopy, EPR, N₂-TPD, Photoluminescence and Photocurrent were used to characterize the prepared catalysts. The results indicate that HCl treatment does not influence the crystal phase of g-C₃N₄ but change the morphology and optical property, leading to the smaller particle size, larger surface area and increased bang gap energy. It is deduced by N₂-TPD, Photoluminescence, Photocurrent and DFT simulations that the nitrogen vacancies formed by the HCl treatment not only serve as active sites to adsorb and activate N₂ molecules but also promote interfacial charge transfer from g-C₃N₄to N₂ molecules. The HCl treated g-C₃N₄ catalyst exhibits outstanding nitrogen photofixation ability under visible light, which is 13.4-fold higher than that of bulk g-C₃N₄ without nitrogen vacancy. The possible reaction mechanism is proposed.