SiO2-coated pure anatase TiO2 catalysts for enhanced photo-oxidation of naphthalene and anthracene

Abstract

Our current efforts reveal the preparation of SiO2@TiO2 nanocomposites having different thicknesses of silica shell and the relationship to photocatalytic activity (PCA) for the photo-oxidation of naphthalene and anthracene. The presence of SiO2 coating over TiO2 surface was demonstrated by FT-IR analysis, with peaks corresponding to SiOSi (1081cm−1) and SiOTi (950cm−1) bonds observed. High-resolution transmission electron microscopy analysis confirmed the presence of SiO2 in the as-prepared nanocomposites and the amount of Si, Ti, and O was determined by energy dispersive X-ray spectroscopy analysis. Increasing the SiO2 shell thickness increases the surface area of the nanocomposites (69–235m2/g), which enhances naphthalene/anthracene adsorption. However, the observed PCA trend presents an inverse correlation to the adsorption studies, where the as-prepared samples possessing the highest surface areas exhibited the least PCA, while catalysts having lower surface areas (among silica coated samples) displayed the highest PCA in the degradation of naphthalene and anthracene to CO2. Despite complete degradation of naphthalene and anthracene, incomplete mineralization occurred, ascribed to the formation of various intermediates, identified by GC–MS analysis.