The photocatalytic performance of g-C^sub 3^N^sub 4^ from melamine hydrochloride for dyes degradation with peroxymonosulfate

Graphitic carbon nitride materials (g-C3N4) were prepared from melamine hydrochloride under different calcination temperatures, and were investigated as metal-free catalysts for Acid Orange 7 degradation in the presence of peroxymonosulfate (PMS) under visible light. It was found that with the increase of calcination temperature, the morphological features of g-C3N4 change from a typical flat layer structure with numerous mesopores to a thinner platelet-like structure, accompanied by the increase of BET surface area. The increase of heating temperature can also enlarge the band gap of g-C3N4. But under a higher temperature of 600 °C, the band gap is significantly reduced, probably due to the decrease of the structure defects. The obtained samples can effectively activate PMS under visible light irradiation to generate reactive species such as sulfate radicals, superoxides and photogenerated hole for dye degradation. Compared with the samples obtained from melamine, the activity is much higher, attributed to the dramatic enhancement of BET surface area. The catalysts also present a long-term stability during multiple runs. The effect of several reaction parameters and the formation of intermediates were also discussed. This study can improve our understanding of PMS activation on g-C3N4 catalysts under visible light for pollutants removal.