Photocatalytic Oxidation of Benzene to Phenol and Dye Over N and S Doped Ferromagnetic Nanosize TiO2

Abstract

In the present investigation, we report the presence of N, S, and Ti³⁺ in the TiO₂ samples, and the surface exhibits acidic characteristics. The synthesized TiO₂ samples were also found to be ferromagnetic at room temperature and show higher photocatalytic activity compared to commercially available TiO₂ (DP-25). Nano-sized TiO₂ with a high surface area was obtained through a simple sol-gel synthesis method, using hydrazine sulfate as fuel during synthesis. The synthesized TiO₂ was found to contain N and S doping, with surface defects present due to cationic and anionic vacancies. The presence of defects was confirmed by Raman spectroscopy, infrared (IR) spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDAX), and photoluminescence (PL) analysis. The presence of Ti³⁺ in the TiO₂ samples was confirmed by Electron Spin Resonance spectroscopy (ESR) and X-ray Photoelectron Spectroscopy (XPS). XPS also revealed nitrogen and sulfur doping in the TiO₂ samples. The synthesized TiO₂ possesses an acidic surface, and surface acidity was measured through pyridine adsorption and ammonia-Temperature-Programmed Desorption (NH₃-TPD) studies. The ferromagnetic behavior of the synthesized samples was confirmed by Vibrating Sample Magnetometer (VSM) measurements. The synthesized samples were further studied for their photocatalytic activity in methylene blue dye degradation, 4-nitrophenol degradation, and photo-oxidation of benzene to phenol. We report the synthesis of TiO₂ with simultaneous nitrogen and sulfur doping, exhibiting ferromagnetism and high activity toward photocatalytic oxidation reactions.