One‐step flame synthesis of SnO₂ / TiO₂ composite nanoparticles for photocatalytic applications

Abstract

SnO 2 / TiO 2 composite nanoparticles have been synthesized in a single‐step by feeding evaporated precursor mixtures into an atmospheric pressure diffusion flame. Particles with controlled Ti: Sn ratios were produced at various flow rates of oxygen, and the resulting powders were characterized by BET surface area analysis, XRD, TEM, EDAX and UV‐Vis spectroscopy. For the lowest concentration (3.4 mol %) of SnO 2 employed in this study anatase phase of TiO 2 is stabilized, while segregation of SnO 2 is seen at medium (6.9 to 12.4 mol %) and high concentrations (20.3 mol %). Though the equilibrium phase diagram predicts complete solubility of one oxide in another at all compositions, segregation of SnO 2 phase is observed which is explained by the usage of diffusion flame in the present study. The particle formation mechanism of SnO 2 / TiO 2 composites is proposed basing on the single component aerosol formation. Photocatalytic activity of the composite particles is tested for the degradation of methylene blue and is compared with pure TiO 2 synthesized under similar conditions. Improved photocatalytic activity of the composite particles is attributed to the stabilized anatase phase and better charge separation due to the coupling of TiO 2 and SnO 2 within the composite nanoparticles.