1,2-Diolates of titanium as suitable precursors for the preparation of photoactive high surface titania

Abstract

1,2-Diolates of titanium of stoichiometric formula [Ti(OCHRCH 2O) 2] (R = −H, −CH 3, −CH 2CH 3) were prepared by reacting a titanium source (titanium(IV) isopropoxide (TIP) or titanium(IV) chloride) with an excess of the respective 1,2-diol. The diol was employed in a great excess; no other solvent was present in the synthesis procedure. The titanium diolates obtained have a white powder appearance and show a high degree of crystallinity as deduced from powder X-ray diffraction. It has been observed that their stability towards moisture is determined by the R group (R = −H, −CH 3, −CH 2CH 3). Hydrolysis of these titanium 1,2-diolates in water was a simple way to produce high surface porous titania with BET surface area up to 300 m 2 g −1. These as-synthesised titania contain anatase crystallites and show photocatalytic activity versus formaldehyde degradation prior to calcination. Nevertheless, the decomposition rate of formaldehyde increased notably when titania samples were annealed at 773 K. This thermal treatment increases their crystallinity at the expense of a BET surface area decrease down to 75 m 2 g −1 or less. The photocatalytic performance of the annealed samples is superior than that of commercial TiO 2 (Degussa P-25, Hombikat UV-100).