Sulfur-Doped Mesoporous Carbon Nitride Decorated with Cu Particles for Efficient Photocatalytic Degradation under Visible-Light Irradiation

Three simultaneous strategies were successfully combined, for the first time, in one material including sulfur doping, creating a mesoporous structure, and deposition of Cu element as a low-cost non-noble metal to modify the internal and external surfaces of carbon nitride framework. For this purpose, sulfur-doped mesoporous graphitic carbon nitride (MCNS) materials were synthesized from thiourea as a low cost precursor and SiO 2 gel solution as a template through a thermal condensation method. A series of copper deposited MCNS (Cu/MCNS) with Cu nominal loadings from 4 to 9 wt % were fabricated by a facile precipitation-reduction method, and the resulting samples were utilized in the photocatalytic degradation of methyl orange (MO) as a hazardous dye in aqueous solution under visible-light irradiation. Phase structures, morphologies, and textural, optical, as well as photoelectrochemical properties of Cu/MCNS photocatalysts were well characterized. Results indicated that synergistic effects of the sulfur doping, mesostructure, and especially the presence of Cu particles on the surface of MCNS extended the visible-light harvesting ability and facilitated the separation of photogenerated electron–hole pairs, and therefore, the photocatalytic activity was dramaticaly enhanced. The optimal Cu nominal loading value was determined to be 7 wt %, and the corresponding degradation rate of MO was about 100% during 90 min under the optimized operating variables conducted by the response surface methodology. In addition, the photocatalyst showed high reusability and stability without any significant decrease in its performace. Based on the trapping experiments results, the h + and •O 2 ¯ radicals as the predominant active species were responsible for the oxidation of MO over the Cu/MCNS catalyst under visible-light irradiation.