Preparation of meso-porous TiO2 gels and their characterization

Mesoporous TiO2 gels, which are attractive for their potential application to photocatalysts and electrodes for wet solar cells, have been prepared by a newly developed method and their microstructure was investigated. Monolithic gels were obtained by hydrolysis of Ti(n-C4H9O)4 in an ethanol/ethylacetoacetate solution. The wet gels were aged and dried after immersion in an ethanol solution of surfactants, cetyltrimethylammonium chloride (CTAC) or benzyltrimethylammonium chloride (BTAC) (CTAC- or BTAC-modified xerogels). The organic substances in the gels can be removed by heating up to 500°C in air. After calcination at 600°C, emanation thermal analysis (ETA) and N2-adsorption measurements were made. The BET surface area, the pore volume and the pore size increased as a result of surfactant modification. The most probable pore radius of the xerogel, BTAC-modified gels and CTAC-modified gel was 2.4, 2.8 and 5.0 nm, respectively. The pore size distribution of mesoporous TiO2 gels depends on the size of surfactant micelles. The microstructure of mesoporous gels can be characterized by ETA. The 220Rn-release rate of the samples labelled with 228Th and 224Ra during heating was xerogel<BTAC-modified gel<CTAC-modified gel. The 220Rn release rate depends on the pore size of the gels as well as the surface areas.