Effect of sulfation on the photoactivity of TiO2 sol-gel derived catalysts

Titania and sulfated-titania were prepared by the sol-gel method using titanium alkoxide as titania precursor. BET specific surface areas on samples calcined at 600 degreesC were 57 and 62 m(2)/g for titania and sulfated-titania, respectively. FTIR spectra of sulfated samples show the 1360-1370 cm(-1) absorption band assigned to S=O vibrations. Moreover, by means of FIFIR-pyridine absorption the strength of the sulfate bonded on the TiO2 surface was studied. Pyridine absorption bands assigned to Lewis and Bronsted acidic sites were identified on sulfated TiO2. A diminution of the band gap (E.) by effect of sulfation was observed by UV-Vis spectroscopy. X-ray diffraction patterns show that sulfate ions stabilize the anatase phase. The photoactivity of the samples determined in the 2,4-dinitroaniline decomposition was found to be higher in sulfated samples. A model is proposed, in which the sulfate anchored to the titania surface acts as an electron trap during photo activation leading to an enhancement of activity. (C) 2002 Elsevier Science B.V. All rights reserved.