Hierarchical macro/mesoporous TiO2/SiO2 and TiO2/ZrO2 nanocomposites for environmental photocatalysis

Photocatalytic purification methods for polluted air and wastewater show great promise for environmental remediation, allowing the "green'' mineralization of organic pollutants under ambient conditions. The creation of macro/mesopores in semiconductor photocatalysts has been found to improve the overall photocatalytic efficiency, but porous systems are generally unstable against thermal sintering, which is indispensable for removing organic templates and enhancing structural crystallization. In this study, we employed nanosized ZrO2 and SiO2 as structural modifiers to improve the structural stability in a macro/mesoporous TiO2 photocatalyst. This was accomplished by soft-chemical synthesis in the presence of surfactants, followed by calcination at high temperatures. The resulting porous TiO2-based nanocomposites not only feature enhanced textural properties and improved thermal stability, but also show an improvement in photocatalytic activity over pure TiO2. The introduction of a secondary phase imparts the additional functions of improved surface acidity and extra binding sites onto the porous structures. The favorable textural properties, along with the improved surface functions contribute to the high photocatalytic activity of catalysts calcined at high temperatures.