Low-temperature solvothermal synthesis of visible-light-responsive S-doped TiO ₂ nanocrystal

In this work, a low-temperature solvothermal method has been developed to synthesize visible-light-responsive S-doped TiO ₂ nanocrystal photocatalyst, using thiourea as the sulfur source to enhance sulfur incorporation into TiO ₂ lattice. The effects of different S:Ti molar ratio on the crystal structure, chemical composition, surface property and catalytic performance have been studied. X-ray photoelectron spectroscopy (XPS) analysis and Fourier transform infrared (FT-IR) spectra displayed that the TiO ₂ was modified by the S element incorporated into the TiO ₂ network to form TiOS bond, which therefore led to the formation of intermediate energy level just above the O 2p valance band, and caused the absorption edge of TiO ₂ to shift into the visible light region up to 500 nm. Characterization results show that the pure nanocrystal anatase structure, with both the degree of S doping and oxygen vacancies makes contribution to the exceptional photocatalytic activity of TONS in visible-light degradation of Methylene Blue (MB) and phenol molecules.