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

Abstract

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.