Nitrogen and Sulfur Quantum Dot Co-Modified Graphene Nanosheet with Enhanced Photocatalytic Activity for Methyl Orange Degradation

Nitrogen-sulfur quantum dot co-modified graphene nanosheets composites (NSG) were fabricated via a facile hydrothermal method as a high performance metal-free catalyst for methyl orange (MO) degradation. Physical-chemical properties of the obtained samples were characterized by XRD, FTIR, SEM, TEM, EDX, TGA, BET, and UV–Vis DRS technologies. Compared with RGO, NSG exhibited much better photocatalytic performance for MO degradation under visible light, especially, NSG(30) showed the best photocatalytic degradation rate of 100% within 180 min. XRD, TG, and UV–Vis DRS results demonstrated that the addition of N and S can enhance the stability of oxygen containing functional groups to supply more adsorption active centers for organic contaminant molecular, adjust the band gap to a certain extent and increase the number of photogenerated electrons, improve the visible light utilization rate of the material and thus improve the photocatalytic degradation performance of the NSG composites. The degradation activity of the catalyst remained above 90% after 3 recycles. Finally, a possible photodegradation mechanism of MO on the obtained NSG sample was proposed.