A comprehensive study of the synthesis, characterization and activity of TiO2 and mixed TiO2/SiO2 photocatalysts

The use of titania–silica materials in photocatalytic processes has been proposed as an alternative to the conventional TiO2 catalysts, in order to facilitate the separation of the solids after the reaction. However, despite the large number of works in this field, up to date it is not totally clarified the mechanism governing the photocatalytic activity of the mixed TiO2/SiO2 oxides. In the present work, several titania–silica materials have been prepared through a sol–gel method controlling the main variables to obtain materials with different textural properties, degree of titanium incorporation and dispersion of such species and crystallinity of titanium dioxide. Characterization of the samples and correlation with their activity for the photocatalytic oxidation of cyanide has permitted to determine that the main factors conditioning the photoactivity of these materials are: (i) textural properties and accessibility of the titania surface, (ii) formation of anatase nanocrystals of suitable size and band gap energy and (iii) quality of the titania crystal network, improved by the use of a hydrothermal crystallization procedure.