A study on structure, morphology, optical properties, and photocatalytic ability of SrTiO3/TiO2 granular composites

(1-x)SrTiO3-xTiO2 granular composites with x=0.3, 0.4, 0.5, 0.6, 0.7, and 0.8 were synthesized by sol-gel process. Structure, morphology, optical properties, and photocatalytic activity were investigated in detail using x-ray diffraction (XRD) analysis, Raman scattering, field-emission scanning electron microscopy (FE-SEM), Transmission Electron Microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectra, and photoluminescence (PL). XRD analysis showed the formation of single phase for parent phases and the present of two component phases in all composites without any impurity. A tight cohesion between TiO2 and SrTiO3 (STO) at grain boundary region was inferred from lattice parameter change of STO. Moreover, FE-SEM images revealed a granular structure of composite in which SrTiO3 particles were surrounded by smaller TiO2 nanoparticles. As TiO2 concentration increased, absorption edge firstly shifted to the left for composite with x=0.3 and then shifted gradually to the right with further increasing of TiO2 content from 30 mol% to 80 mol%. Composites exhibited a stronger photocatalytic activity than parent phases, with the highest efficiency at 50 mol% of TiO2. PL analysis result showed that the recombination rate of photogenerated electron-hole pairs decreased in composite sample, which partly explained the enhanced photocatalytic property.