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

Abstract Nanocrystalline TiO 2 and Si-doped TiO 2 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 (O 2 , air, and N 2 ). 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 N 2 -treated TiO 2 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 TiO 2 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 TiO 2 and Si-doped TiO 2 , such as surface oxygen and Ti 3+ sites, thus improving photocatalytic activity. The increasing of anatase phase stability and the formation of Ti 3+ sites due to N 2 -treated and Si-doped TiO 2 nanocatalyst promoted the photocatalytic activity of MB degradation.