The pore structure of meso- and microporous TiO2-membranes

The analysis of fine-pored materials becomes increasingly difficult as the pores get smaller because more and more assumptions regarding the pore shape must be included in the interpretation of the analysis results. Reliable information can only be obtained by combining different methods of analysis. In this paper, systematic analyses, of mesoporous and microporous TiO2 layers are presented. Test filtration with molecular mass standards in combination with mercury porosimetry and nitrogen sorption proved particularly suitable. The findings obtained regarding pore shape and pore size were compared with high-resolution electron microscope images. It could be shown that the pores in mesoporous TiO2 membranes, which had been prepared in a colloidal sol-gel process, are slit-shaped and have a diameter of 5 nm. In contrast, microporous TiO2 membranes, which had been produced in a polymer sol-gel process, contain cylindrical pores with a pore diameter of 0,9 nm.