Preparation of highly ordered cubic mesoporous WO₃/TiO ₂ films and their photocatalytic properties

Highly ordered cubic mesoporous WO₃/TiO₂ thin films were prepared by spin coating via an evaporation-induced self-assembly (EISA) process, employing metal alkoxides as inorganic precursors and Pluronic F127 as a structure-directing agent. With the incorporation of WO₃ into TiO₂, the ordering of the mesopore structure has been appreciably improved. That is, the presence of 2-6 mol % WO₃ retards the crystallization to the anatase phase, and this leads to the relative stabilization of the mesopore structure. The characterization results suggest that the majority of incorporated W species are located at the surface of the mesopore wall instead of doping into the TiO₂ lattice. For the prepared cubic mesoporous WO₃/TiO₂ thin films, the photocatalytic activity in decomposing 2-propanol in the gas phase was optimized at 4 mol % of WO₃ concentration. Its photocatalytic activity was 2.2 times that of a mesoporous TiO₂ film and 6.1 times that of a nonporous TiO₂ film derived from a typical sol-gel method. The enhanced photocatalytic activity of WO₃/TiO₂ is ascribed to the increase in surface acidity.