Sulfur-Doped g-C3N4 with Enhanced Visible-Light Photocatalytic Activity

The S-doped g-C3N4 materials were prepared by heating mixtures of urea and thiourea with various weight ratios at 550 °C, and denoted as x:y SCN, where x:y is weight ratios of urea to thiourea. The obtained samples were characterized by X-ray diffraction, diffuse reflectance ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric differential thermal analysis, scanning electron microscopy and infrared spectra. The results showed that all the x:y SCN materials exhibit the presence of doping S in the structure of g-C3N4 and higher capability in the photodegradation of Rhodamin B in aqueous solution under visible light condition than pure g-C3N4. Among the SCN samples, 75:25 SCN performed the highest photocatalytic activity, which is believed the presence of the largest amount of doping S in the matrix of g-C3N4, leading to reduction of their bandgap. The reduction of bandgap for S-doped g-C3N4 materials compared to pure g-C3N4 was proved by theoretical calculation.