In situ fabrication of SnO2/S-doped g-C3N4 nanocomposites and improved visible light driven photodegradation of methylene blue

Abstract

Herein, several Sn/CNS composite photocatalysts consisted of SnO2 and sulfur-doped graphitic carbon nitride (CNS) were in situ fabricated through thermal condensation of thiourea and tin(IV) chloride as starting materials. The synthesized Sn/CNS photocatalysts with different SnO2 contents (1.6, 7.7 and 8.5wt%) were characterized by several techniques. The phase structures and morphology results of composite indicated that the perfect crystalline structure and the stacking degree of CNS phase were disrupted during the formation of SnO2 particles, so that specific surface area of composite was enhanced about 2.8 times compared with that of pure CNS photocatalyst. The optimized photocatalyst, i.e. SnO2(7.7)/CNS composite, showed the highest photocatalytic efficiency for degrading methylene blue (MB) under visible light irradiation among the individual CNS and SnO2 photocatalysts. The improved photoactivity could be related to introducing S dopant in CNS backbone which led to increasing the visible light absorption. Besides, due to loading the SnO2 nanoparticles, heterojunctions were formed between SnO2 and CNS which facilitated the effective charge transfer through interfacial interactions between both components. The heterojunction prepared by the in situ strategy illustrated excellent stability for the photocatalytic activity under optimized conditions obtained by response surface methodology (RSM) method. It may be attributed to the strong surface interaction between individual components during evolution of CNS structure. It was also found that •O2− was the main reactive species in the degradation reaction and a possible mechanism for the enhanced photocatalytic activity of the SnO2(7.7)/CNS composite was discussed in detail.