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. Synthesized TiO₂ samples were also found to be ferromagnetic in nature at room temperature and show high photocatalytic activity in comparison to commercially available TiO₂ (DP-25). Nanosize TiO₂ with a high surface area was obtained by a simple sol-gel method of synthesis and during the synthesis hydrazine sulphate was used as fuel. Synthesized TiO₂ was found to be with N and S doping and surface defects were present due to cationic and anionic vacancies. The presence of defects was confirmed from the Raman, Infra-Red (IR), Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM-EDAX), Photoluminescence (PL) analysis. The presence of Ti³⁺ in the TiO₂ samples was confirmed by the Electron Spin Resonance spectroscopy (ESR) and X-ray Photoelectron Spectroscopy (XPS) Spectra. XPS also showed the presence of nitrogen and sulphur doping in the TiO₂ samples. Synthesized TiO₂ possesses an acidic surface and surface acidity was measured from the pyridine adsorption and Ammonia-Temperature Programme Desorption (NH₃-TPD) studies. The ferromagnetic behavior of the synthesized samples was confirmed by the Vibrating Sample Magnetometer (VSM) measurements. Synthesized samples were further studied for their photocatalytic activity towards methylene blue dye and 4-nitrophenol degradation and for photo-oxidation of benzene to phenol conversion. We report the synthesis of the simultaneous presence of nitrogen and sulphur doping in the ferromagnetic TiO₂ and its high activity toward photocatalytic oxidation reactions.