Titanium and zirconium-based mixed oxides prepared by using pressurized and supercritical fluids: On novel preparation, microstructure and photocatalytic properties in the photocatalytic reduction of CO2

Abstract

The ZrxTi1-xOn mixed oxides with various Ti:Zr molar ratios and parent TiO2 and ZrO2 were prepared unconventionally, combining the reverse micelles-controlled sol-gel method with high-pressure processing by pressurized and supercritical fluids. The mixed oxides were characterized using several complementary characterization methods and investigated in the photocatalytic reduction of CO2. Applied novel unconventional processing affected significantly the (micro)structure of mixed oxides, which was further reflected to their optical and thus electronic properties. The Zr-0.1 Ti-0.9 O-n mixed oxide showed the best photocatalytic behavior in a consequence of the optimal crystallinity and the lowest band gap energy from all mixed oxides. The Zr0.1Ti0.9 O-n mixed oxide was of bicrystalline TiO2 anatase-brookite structure (67:33 wt.%) showing small crystallite-sizes, which allowed the optimal surface phase junction.