Impact of calcination atmospheres on the physiochemical and photocatalytic properties of nanocrystalline TiO2 and Si-doped TiO2

Abstract

Nanocrystalline TiO2 and Si-doped TiO2 samples were prepared by solvothermal and sol–gel methods. Before the characterization and photocatalytic test, the thus-obtained powder and gel were calcined under different atmospheric gas flows (O2, air, and N2). The physiochemical properties of the samples were determined using X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–vis), electron spin resonance (ESR), transmission electron microscope (TEM), energy dispersive X-ray spectrometer (EDX) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was evaluated by the degradation of methylene blue (MB) dye under UV and visible light irradiation. The solvothermal-made N2-treated TiO2 nanocatalyst showed the highest photocatalytic activity under both UV and visible light irradiation. The addition of Si resulted in the formation of partial monolayer of Si on TiO2 nanocatalyst and an increase of the anatase phase stability. The ESR and XPS results reveal that the calcining atmosphere affected the distribution concentration of surface and interface species in TiO2 and Si-doped TiO2, such as surface oxygen and Ti3+ sites, thus improving photocatalytic activity. The increasing of anatase phase stability and the formation of Ti3+ sites due to N2-treated and Si-doped TiO2 nanocatalyst promoted the photocatalytic activity of MB degradation.