The activation and conversion of carbon dioxide on the surface of zirconia-promoted ceria oxides

Abstract This study reports the conversion of carbon dioxide (CO2) by ceria (CeO2)-zirconia (ZrO2) composites with various ZrO2 contents (0, 20, 50, 80 and 100%). The modification introduced by ZrO2 altered the structural properties of the ceria samples, affecting their reducibility and subsequent activity to convert CO2. The characterisation results showed a clear relationship between the structural properties of the materials and the activity for CO2 conversion. The addition of ZrO2 was effective to improve a close interaction between CeO2 and ZrO2 and induced the formation of structural defects that further promoted oxygen transport and facilitated the creation of oxygen vacancies that were critical for CO2 conversion. All samples investigated were found to be effective in converting CO2 into carbon monoxide (CO) at 450 °C, and the addition of ZrO2 was also found to be effective in improving the thermal resistance and stabilising the crystalline structure of the samples especially when the ZrO2 content was > 50%. When the content of ZrO2 controlled between 50% and 80%, the onset temperature for CO2 conversion was found to be 285 °C, which was about 80 °C lower than that required for the sample without ZrO2 modification. Thus, modifying CeO2 by ZrO2 was effective to prevent both the textural and structural alteration of the samples under a high temperature environment as well as cyclic redox operations, resulting in a constant and high degree of CO2 conversion into CO.