Understanding the role of catalytic active sites for heterogeneous photocatalytic oxidation of methanol and thermal reduction of NOx

Abstract

Identification and understanding the role of catalytic active sites are crucial to realize the performance of a catalyst. The conventional heterogeneous metal catalysts are still far away from the understanding of the nature of active sites. In this work, the solid solutions of Ti1-xPtxO2-δ (x = 0.01, 0.03, and 0.05) were synthesized by a microwave assisted hydrothermal method, where bivalent Pt was doped into the lattice of TiO2 in order to create the oxide ion vacancies. The as-prepared materials were reduced to leach out the substituted Pt in metallic state. Both the sets of materials were thoroughly characterized structurally and morphologically. The catalytic role of Pt was probed in these materials for two different and quite important reactions; room temperature photo-oxidation of methanol to hydrogen, and thermal reduction of NO to N2. The active sites of the catalysts were identified from the experimental observations. The elementary reaction mechanism over the active sites were proposed, and supported with modelling. The results revealed that the oxidized and the reduced catalyst behave in a completely different manner in the oxidation and reduction reactions chosen in this work.