Step response and transient isotopic labelling studies into the mechanism of CO oxidation over La0.8Ce0.2MnO3 perovskite

The mechanism of CO oxidation over La0.8Ce0.2MnO3 perovskites has been studied using step response analysis. As these materials pair a high catalytic activity with high hydrothermal stability, perovskites are well-known full oxidation catalysts and form a potential alternative to Pt–Rh based three-way catalysts. Transient isothermal reduction and oxidation studies demonstrate the full reversibility of oxygen uptake at temperatures of 473K and higher. Using isotopically labelled O2, the participation of oxygen from the perovskite lattice could be demonstrated. It is proposed that stable species—most likely bidentate carbonates—are retained on the reduced oxide surface. The highly defective perovskite structure enables rapid exchange between oxygen atoms from surface carbonate and perovskite lattice oxygen. CO oxidation towards CO2 tentatively proceeds through the Eley–Rideal (ER) followed by Langmuir–Hinshelwood (LH) mechanism. In steady state conditions, the formation of CO2 is most likely trough the formation of intermediate carbonate since considerable amounts of C16O16O and C18O18O are formed.