Influence of Post-Synthesis Modifications of Ti 1- x Zr x O₂ Nanocrystallites on Their Photocatalytic Activity for Toluene and Methylcyclohexane Degradation.

The modification of the structural and surface characteristics of Ti1-xZrxO2 nanocrystallites by post-synthesis treatments is revealed as an effective way to enhance their photocatalytic activity. Starting with the same batch of mixed oxide prepared from reverse microemulsions, different photocatalysts have been obtained by either solvothermal treatment, calcination or a combination of both. Extensive physicochemical characterization of the resulting materials shows that solvothermally treated oxides present lower crystallite size and larger surface area, although without previous calcination these samples appear to have a higher degree of structural disorder. These differences are sharply reflected in the changes in photocatalytic activity for the removal of methylcyclohexane (MCH) and toluene vapours at relatively high concentrations. Thus, the best performance for MCH elimination is obtained with the photocatalysts prepared by calcination and subsequent solvothermal treatment. Following this procedure, the resulting Ti1-xZrxO2 material presents larger surface area and high Zr surface concentration with minimal disturbance of the anatase structure. In contrast, for toluene photooxidation, the solvothermally prepared sample shows improved performance, most likely due to its larger surface area, which contributes to hinder deactivation.