Effect of the C and S additives on structural, optical, and photocatalytic properties of TiO₂

Nanoscale composite materials based on titanium dioxide, sulphur, and carbons were obtained. The samples were characterized using X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller and Barret–Joiner–Halenda methods, electron paramagnetic resonance spectroscopy, and ultraviolet–visible and infrared spectroscopy. X-ray powder diffraction revealed the phase of anatase in all composites and appearance of rutile phase for samples with high sulphur content. It was established that composites consist of nanoparticles ca. 6–10 nm. Analysis of nitrogen adsorption–desorption isotherms for the synthesized samples showed the presence of a hysteresis loop which is the evidence for mesoporous structure of the powders. Absorption spectra of nanocomposites showed a bathochromic shift compared with the absorption band of pure TiO₂. It was found that modification of titanium dioxide with sulphur and carbons leads to bandgap narrowing of composites. Nanocomposite samples showed higher photocatalytic activity in the destruction of safranin T under ultraviolet and visible irradiation compared to pure titanium dioxide. It can be connected with the participation of additives in the inhibition of electron–hole recombination, prolongation of charges lifetime, increasing of efficiency of interfacial charge separation, and formation of doping electronic states.