Role of SiO2 in synthesis of SiO2-supported CeO2 composites

Pure and SiO2-supported CeO2 samples were prepared by Ce(NO3)3 decomposition, precipitation, and sol-gel methods in an attempt to study the role of SiO2 in the synthesis of these materials. During synthesis process, SiO2 support uniformly adsorbed cerium ions in aqueous solution, preventing nucleation and crystal growth of CeO2 during the subsequent water evaporation and calcination steps. Uniform adsorption and inhibition were enhanced by NH4+ and, to a larger extent, C5H7O5COO-. Despite the dispersion of cerium ions on SiO2 reduced the temperature at which CeO2 was formed, crystal size and crystallinity of CeO2 in composites were significantly lower than that of pure CeO2 sample prepared by the same synthesis method and at the same temperature. Composites were quite stable upon increasing the temperature from 400 to 800 °C. Visible light absorption, reduction, and photocatalytic activity characteristics of CeO2 were improved upon dispersion on SiO2. This work can help synthetize supported oxides with high activity and thermal stability.