Role of Surface Adsorption in Fast Oxygen Storage/Release of CeO2 - ZrO2 Mixed Oxides

Four kinds of CeO2-ZrO2 mixed oxides, i.e., a physical mixture of ceria and zirconia (CZP), zirconia-coated ceria (ZCC), ceria-coated zirconia (CCZ) and a chemical mixture of ceria and zirconia (CZC), were prepared. The oxygen storage capacity (OSC) measurements at 500 °C were performed under transient and stationary reaction conditions. All the curves of CO2 evolution during CO-O2 cycles presented a bimodal shape. The first peak was primarily the result of the reaction of CO with the oxygen from the oxides, which was mainly determined by the nature of the material. The second peak was mostly related to the CO2 adsorption behavior and was highly influenced by the surface area and the number of surface active sites. As a result, OSC activity of the samples followed in the order of CZC > CCZ > ZCC ≈ CZP.