Creation of redox adsorption sites by Pd2+ ion substitution in nanoTiO2 for high photocatalytic activity of CO oxidation, NO reduction, and NO decomposition

The present study aims at developing a new photocatalyst for NO reduction and CO oxidation by creating redox adsorption sites and utilizing oxide ion vacancy in titania. For this purpose, Pd ion-substituted TiO2, Ti1-xPdxO2-delta, was synthesized for the first time by solution combustion method. The photocatalytic activity was investigated with increasing Pd substitution and the optimum concentration was found to be 1 atom % Pd ion in TiO2. The reduction of NO was carried out both in the presence and in the absence of CO. Despite competitive adsorption of NO and CO on the Pd2+ sites, the reduction of NO was 2 orders of magnitude higher than unsubstituted TiO2. High rates of photooxidation of CO with O-2 over Ti1-xPdxO2-delta are observed at room temperature. It was shown that enhanced CO oxidation at Pd2+ ion site and O-2 or NO photo dissociation at oxide ion vacancy is responsible for the enhanced catalytic activity.