The effect of n–π* electronic transitions on the N2 photofixation ability of carbon self-doped honeycomb-like g-C3N4 prepared via microwave treatment

Light harvesting is an important part of the photocatalysis process. In this work, carbon self-doped honeycomb-like g-C3N4 with outstanding N2 photofixation ability was prepared via microwave treatment. XRD, N2 adsorption, UV-Vis, SEM, XPS, ESR and PL were used to characterize the as-prepared catalysts. Combining the carbon self-doping with microwave treatment, the n–π* transition was successfully stimulated. The remarkable red shift of absorption edge from 465 nm to near 600 nm was observed, leading to the obviously promoted visible light absorption. The synergy effect of carbon doping and microwave treatment also enhances the surface area and separation efficiency of electron–hole pairs. The as-prepared catalyst displays the highest NH4+ concentration of 5.3 mg L−1 gcat−1, over 11 times higher than that of neat g-C3N4, as well as excellent photocatalytic stability. DFT calculation was also used to further prove our point of view. This paper provides a new way for the construction of high efficiency photocatalysts.