Experiments and DFT investigation of microwave-assisted sol–gel method prepared S-doped g-C3N4 for enhanced photocatalytic degradation of gaseous toluene

Abstract

Volatile organic compounds (VOCs) are hazardous to human health and have a negative impact on productivity. Photocatalytic oxidation process is one of the most promising techniques for removing indoor VOCs. Here, S-doped g-C₃N₄ was synthesized using a high-pressure microwave-assisted sol–gel method. Toluene removal by S-doped g-C₃N₄ with a S/g-C₃N₄ mass ratio of 1 : 1 was nearly 100% after 180 min of UV irradiation or 360 min of visible light irradiation. S-doping reduces layer spacing and causes the formation of g-C₃N₄ lattice defects, allowing the photo-generated electron–hole pairs to be separated more effectively. The S-doping ratio is optimized to strike a favorable compromise between improving the photo-generated electron–hole separation efficiency and lowering the surface electron conductivity. DFT calculations was performed to analyze the energy band structure and electronic properties of S-doped g-C₃N₄ to explain the mechanism of S-doping to enhance the photocatalytic activity of g-C₃N₄. S-doped g-C₃N₄ has efficient catalytic activity and excellent photo-corrosion resistance, suggesting a potential practical application for VOC removal.