The characterization of mixed oxides of TiO2/SiO2 and TiO2/Al2O3 prepared by sol-gel methods is described. Application of the TiO2/Al2O3 material for the photocatalytic decomposition of salicylic acid gave improved activity relative to TiO2-only materials. The photocatalytic activity of TiO2/SiO2, TiO2/Al2O3, and TiO2 toward the photocatalytic decomposition of phenol demonstrated the enhancement of local TiO2 sites on TiO2/SiO2 materials relative to the other materials. The characterization of the catalysts indicates that the TiO2/SiO2 materials consist of matrix-isolated TiO2 quantum particles, while the TiO2/Al2O3 materials do not.