Molecular Reactions of O2 and CO2 on lonically Conducting Catalyst

The presence of CO2, an unavoidable component in air and fuel environments, is known to cause severe performance degradation in oxide catalysts. Understanding the interactions between O-2, CO2, and ion-conducting oxides is critical to developing energy-conversion devices. Here, surface reaction kinetics of Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) with the presence of both O-2 and CO, is determined using gas-phase isotope exchange. BSCF actively reacts with CO2, and the incorporation of oxygen from CO2 to the lattice of BSCF is directly observed as low as 50 degrees C. Above 200 degrees C, the reaction between CO2 and the BSCF surface dominates and is independent of the oxygen partial pressure. In addition, CO2 competes with O-2 for binding to vacancy sites, forming surface intermediate species. Surprisingly, these surface intermediate species offer oxygen to exchange with oxygen in gaseous O-2 and CO2, inhibiting the interactions between O-2 and the solid surface. This work provides fundamental insight into functioning oxide catalysts, and the results can be applied to the design of improved oxide catalysts.