Crystallization of hydrothermally treated TiO2 pillars in pillared montmorillonite for improvement of the photocatalytic activity

A novel pillared clay, i.e. pillared montmorillonite with crystallized TiO2, has been developed as a highly active photocatalyst. The TiO2 pillars in pillared montmorillonite were crystallized to anatase by hydrothermal treatment, while the porosity of the pillared clay was retained. The size of the crystallized TiO2 pillars and the average pore diameter showed good agreement, and both sizes could be controlled in the range ca. 40-90 Angstrom by changing the treatment conditions. The photocatalytic properties of the TiO2 pillars were investigated in the degradation of trichloroethylene in water. The hydrothermal crystallization enhanced the catalytic activity both per unit weight of TiO2 and per exposed unit surface area of TiO2. The catalytic activity of the TiO2 pillars was also enhanced by quantum-size effects: as the TiO2 pillar size decreased, the pillared montmorillonites exhibited higher catalytic activity and showed larger blue-shifts in their UV absorption spectra.