Photocatalytic activity of structured mesoporous TiO₂ materials

Starting from colloidal TiO₂ nanoparticles in combination with tetraethyl orthosilicate using neutral Pluronic or cationic cetyltrimethylammonium as templates, a series of structured mesoporous silicas has been obtained. The structure of the mesoporous titania was confirmed by isothermal gas adsorption, transmission electron microscopy, and X-ray diffraction. The pore diameter ranged between 3.8 and 10.9 nm, and the BET surface area varied from 99 to 584 m² g^-1. The photocatalytic activity of these samples for the degradation of phenol in aqueous solution has been compared with that of standard P-25 TiO₂. Even though the activity of these new mesostructured materials is lower that those found for P-25 TiO₂, the turnover frequency of the photocatalytic activity (moles of phenol degraded per Ti atom present at initial reaction time) is much higher for the mesoporous titania, particularly with low titanium contents for those materials (mpTiO₂-5 and TiO ₂-SBA15-5).