Role of surface-purity in photocatalytic activity of nanocrystalline anatase-titania processed via polymer-modified sol-gel

Nanocrystalline titania powders have been synthesized via conventional and modified sol-gel using an alkoxide precursor for different R, the ratio of molar concentration of water to that of alkoxide precursor, and calcination temperature. The apparent first-order reaction rate-constant obtained for the powder synthesized via conventional sol-gel is comparable with that of commercial Degussa-P25. Conventional sol-gel has been modified using the hydroxypropyl cellulose polymer to increase the specific surface area of the photocatalyst; and hence, to further enhance its photocatalytic activity. Although higher specific surface area and smaller average nanocrystallite size have been obtained for the powders synthesized via modified sol-gel, they exhibit reduced photocatalytic activity relative to that of powders synthesized via conventional sol-gel. The deactivation of the present photocatalyst has been explained on the basis of reduced surface-purity of the powders after processing via modified sol-gel as induced by the presence of surface-residual organic compounds.