Bare and Pt-loaded LaCo1-xFexO3 perovskites as catalysts for CO-PROX reaction

Abstract

Perovskites based on cobalt and iron LaCo1-xFexO3 (x = 0, 0.1 and 1) and their behavior in the presence of platinum yPt/LaCo1-xFexO3 (y = 0.1, 0.5 and 2.5% wt.) were evaluated as catalysts in the preferential oxidation of carbon monoxide (CO-PROX). Perovskites (general formula ABO3) are alternative materials to conventional transition metal oxides, expanding the tunable redox properties according to the combination of elements. In CO-PROX, Co3O4 and Pt/Fe3O4 are well-studied systems. The superficial Co3+/Co2+ redox pair is highly active. Still, the Co3O4 is easily reduced at low temperatures under the reducing conditions of CO-PROX, forming less active phases enriched in Co2+ and Co0. On the other hand, Fe3O4 is not active but becomes highly reactive when associated with Pt through the redox mechanism intermediated by the Fe3+/Fe2+ pair created at the metal interface. Supported by in situ characterization under reducing conditions and complementary ex situ analyses, we found that the LaCoO3 resembles the Co3O4, and the addition of Fe forming LaCo0·9Fe0·1O3 induced higher stability of the perovskite structure under reducing conditions. The presence of Pt significantly impacted the stabilization of the active sites under CO-PROX conditions depending on the perovskite composition. Finally, the Pt/LaFeO3 catalyst combined the high activity of the Pt/Fe3O4 system with the thermal stability of the perovskite structure.