CO₂ and O₂ Co-Exchange on Multivalent Metal Oxides

Abstract

Understanding the multigas reaction mechanism on metal oxides is vital to advance the design principle for electrodes of energy conversion devices exposed to air. Here, CO2 and O2 co-exchange on two perovskite oxides La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and (La0.8Sr0.2)0.95MnO3±δ (LSM) has been investigated via in situ gas-phase isotopic oxygen exchange. LSCF shows high catalytic activity for heteroexchange of lattice oxygen with oxygen in gaseous CO2, possibly because of a high concentration of oxygen vacancies. The exchange between CO2 and lattice oxygen of LSCF is observed to be as low as 50 °C. Conversely, LSM appears to be relatively inert toward CO2 exchange, and the CO2 exchange reaction occurs over the specific temperature region where surface oxygen vacancies are formed. The isotope exchange results provide insights into the study of multigas reaction mechanism on oxide catalysts.

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“…As can be seen in Figure 5b, the introduction of CO 2 (5 and 10%) further increases polarization resistance of all LSCF based electrodes, presumably due to the competitive absorption of CO 2 and O 2 on the same reactive site of the LSCF surface. 44 After 15 h treatment, the gas was switched back to ambient air again, and it is discovered that the polarization resistance of LSCF/GDC NF falls back to the initial level with tiny fluctuation of 7 × 10 −3 Ω cm 2 , which is almost one order of magnitude lower than that of F-LSCF (5.1 × 10 −2 Ω cm 2 ) and c-LSCF (7.3 × 10 −2 Ω cm 2 ). The result confirms the good regenerability of the material.…”