Photocatalytic Activities of Porous Titania and Titania/Zirconia Structures Formed by Using a Polymer Gel Templating Technique

Abstract

The formation of porous metal oxide networks using mixed titania/zirconia precursor solutions was achieved by a polymer gel templating technique. The inorganic porous materials result from a coating of the initial template with obvious structural similarities between the polymer gel and the final inorganic network. The mixed TiO2/ZrO2 network structures exhibit higher surface areas than a corresponding pure titania network, and in a certain range of metal oxide compositions X-ray amorphous mixed glasses are obtained upon calcination at 500 °C. The photocatalytic efficiencies of the TiO2 and TiO2/ZrO2 networks have been assessed by monitoring the photodecomposition of two organic molecules: salicylic acid and 2-chlorophenol. The TiO2 network was found to exhibit an efficiency of ≈60% and ≈65% of the standard Degussa P25 TiO2 (of nanoparticulate morphology) for the salicylic acid and 2-chlorophenol reactions, respectively. For both photocatalytic reactions the presence of zirconia in the titania network (at a molar ratio of 1:9) resulted in enhanced photocatalytic activity relative to the pure TiO2 network (80% and 100% the efficiency of Degussa P25), which is believed to be due to a number of factors including an increased surface area and a decrease of the anatase to rutile crystal phase transformation. A further increase in the zirconia-to-titania ratio leads to decreased activity as amorphous materials are obtained and zirconia itself does not act as a photocatalyst under the experimental conditions used.