Development of magnetically separable mesoporous N doped TiO2-SiO2 coated Fe3O4 nanomaterial as solar photocatalyst for environmental application

Abstract

The present paper deals with the synthesis of visible light-sensitive, easily separable mesoporous magnetic titania material having Fe3O4 in the core as a solar photocatalyst. Core Fe3O4 was synthesized by two different methods for comparative evaluation. The top titania layer was found to be mesoporous thus providing more active sites. Synthesized materials were characterized by UV-vis, XPS, XRD, TEM, and Raman. Core Fe3O4 prepared from Fe(II) and Fe(III) salts showed higher magnetic moments having nanosized particles. On the other hand, the hydrazine method resulted in the formation of tubular iron oxide having a low magnetic moment. XRD and Raman spectra support the formation of porous anatase phase on the top and below the SiO2 layer properly shielded magnetic core. The final magnetic moment of 7.8 emu in the case of iron oxide obtained from Fe(II) and Fe(III) salts indicates that the magnetic separation by applying an external magnetic field is easy. Nitrogen doping of the top titania layer increases the visible light absorption and photocatalytic efficiency. A comparative evaluation of the photocatalytic decomposition of para-nitrophenol and methylene blue was carried out to observe the effect of N doping. The synthesized material is found to be stable and reusable at least five times without any marked change in the catalytic activity and magnetic moment. The synergistic effect of mesoporosity, the presence of oxygen vacancy, and N doping on titania facilitates the higher rate of MB and p-NP degradation under visible light.