Direct microwave synthesis of graphitic C3N4 with improved visible-light photocatalytic activity

The graphitic carbon nitride (g-C3N4) was rapidly synthesized via direct high-energy microwave heating approach. During the preparation process, only low-cost melamine and artificial graphite powders were used, without any metal catalysts or inert protective gas. The microstructure was investigated by using X-ray diffraction (XRD), Flourier transformed infrared (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The spectra of XRD and HRTEM indicated that the obtained g-C3N4 had a high crystallinity. The optical spectra covering Photoluminescence (PL) and Ultraviolet-visible (UV–vis) were also measured at room temperature. PL peak and UV–vis absorption edge of the g-C3N4 were shown at 455 nm and 469 nm, respectively, indicating visible-light photocatalytic property. Finally, the photocatalytic activity of g-C3N4 was investigated and evaluated as photocatalyst for the photo-degradation of Rhodamine B (RhB) and Methyl Orange (MO) in aqueous solution under visible-light (λ>420 nm) irradiation, respectively. Results indicated that the g-C3N4 sample displayed an excellent performance of removing of RhB and MO due to the improved crystallinity and large surface area of 126 m2/g. After the visible-light photocatalytic reaction for 40 min, the decolorization ratios of RhB and MO reached up to 100% and 94.2%, respectively.