Infrared ray assisted microwave synthesis: a convenient method for large-scale production of graphitic carbon nitride with outstanding nitrogen photofixation ability

Abstract

Nitrogen fixation is the second most important chemical process in nature next to photosynthesis. Both the energy consumption and raw material costs are high for the conventional artificial nitrogen fixation technology, the Haber–Bosch process. Here, we report a convenient infrared ray assisted microwave method for synthesizing graphitic carbon nitride (g-C₃N₄) with outstanding nitrogen photofixation ability under visible light. XRD, N₂ adsorption, UV-vis, SEM, TEM, TPD, EPR, PL and photocurrent measurements were used to characterize the prepared catalysts. The results indicate that microwave treatment can form many irregular pores in the as-prepared g-C₃N₄, which cause an increase in the surface area and promote the separation rate of electrons and holes. More importantly, microwave treatment causes the formation of many nitrogen vacancies in the as-prepared g-C₃N₄. These nitrogen vacancies not only serve as active sites to adsorb and activate N₂ molecules but also promote interfacial charge transfer from catalysts to N₂ molecules, thus significantly improving the nitrogen photofixation ability. The higher nitrogen vacancies concentration of g-C₃N₄ prepared by infrared ray assisted microwave treatment causes more chemical adsorption sites, leading to a higher nitrogen photofixation performance. Moreover, the present process is a convenient method for large-scale production of g-C₃N₄ which is significantly important for practical applications.