Surface and bulk changes of a Pt 1%/Ce_0.6Zr_0.4O₂ catalyst during CO oxidation in the absence of O₂

Abstract

The reduction of a Pt 1%/Ce_0.6Zr_0.4O₂ catalyst by CO in the absence of gaseous oxygen was studied by transient reactivity tests, temperature programmed surface reaction with CO, flow thermogravimetric tests and DRIFTS experiments, in order to obtain information generally on the OSC properties and, specifically, on the mechanism of CO oxidation over both, Pt catalyst and support-only sample (Ce_0.6Zr_0.4O₂). The results of thermogravimetric experiments showed the presence of an induction time in the weight change % of the catalyst, depending on the CO concentration in the gas flow. This induction time could be related to the presence of two oxygen reactive sites. The first one leads to strongly chemisorbed CO₂ or carbonate species, while the second, tentatively related to Pt/support interface sites, generates weakly chemisorbed CO₂ species in reversible equilibrium with gaseous CO₂. The concentration of CO and the presence of a co-feeding of gaseous CO₂ significantly and non-linearly affected the presence and reactivity of these Pt/support interface sites, although the details of this effect should be better understood.