Template-free method for synthesizing sponge-like graphitic carbon nitride with a large surface area and outstanding nitrogen photofixation ability induced by nitrogen vacancies

Nitrogen fixation is the second most important chemical process in nature next to photosynthesis. Herein, we report a convenient template-free method for synthesizing sponge-like graphitic carbon nitride (g-C3N4) with a large surface area and outstanding nitrogen photofixation ability under visible light. X-ray diffraction (XRD), N2 adsorption, UV-vis spectroscopy, N2-Temperature programmed desorption (N2-TPD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and photocurrent measurements were used to characterize the prepared catalysts. The results indicate that solvent species (alcohols) play the most important role in the formation of the porous structure. Methanol-treated g-C3N4 exhibits the highest surface area and nitrogen photofixation ability, which are 15.2-fold and 27.2-fold greater, respectively, than that of untreated g-C3N4. Nitrogen vacancies could activate N2 and promote interfacial electron transfer, thereby significantly improving the nitrogen photofixation ability.