Construction of S-doped MgO coupled with g-C3N4 nanocomposites with enhanced photocatalytic activity under visible light irradiation

In the present work, a series of photocatalysts in which S-MgO (SM) was coupled with g-C3N4 (CN) were synthesized and characterized in detail using various characterization techniques. The photocatalytic performance of the SM/CN for Rhodamine B (RhB) degradation was investigated using visible light irradiation. The results demonstrated that the SM/CN showed better photocatalytic performance than the bare CN. A high photocatalytic degradation efficiency of 97.72% was achieved in 60 min for the SM/CN composites coupled with 1.0 wt% SM, which is much faster than for the bare CN (35.61%). Moreover, three-dimensional excitation-emission matrix (3D EEM) fluorescence spectroscopy showed that the RhB was completely degraded instead of simply being decolorized using the SM/CN composites. Further research confirmed that superoxide radical and hydroxyl radical were the main active species for RhB decomposition. The improvement in the photocatalytic performance could be due not only to the formation of a heterojunction between SM and CN, but also the special surface of SM. Therefore, the SM/CN nanocomposites are efficient and reliable photocatalysts for sewage treatment.