Interactions of water vapor and carbon dioxide with Ca doped ceria surfaces

Abstract

CeO2 is used in a variety of applications in the fields of electrochemistry and catalysis. In order to improve its surface activity, ionic conductivity, and thermal stability for application in these and other fields, the use of dopants such Ca is commonplace. However, whereas the application of Ca as a dopant in CeO2 has received much attention, little to no information can be found on the effects of such Ca addition on the interactions of gases with the surface of Ca-doped CeO2, which are crucial in such fields. In this study, we explored the interactions of environmental gases (i.e., water vapor and CO2) on the surface of Ca-doped CeO2. Addition of Ca to CeO2 was shown to increase gas uptake by approximately 40% and for water vapor and 90% for CO2. This increase in gas uptake is accompanied by an increase in the heat of adsorption from −60.5 to −71.5 kJ/mol in case of water vapor and from −65.3 to −77.8 kJ/mol in case of CO2. The increases in gas uptake and energetics derive from the formation of Ca-based surface phases. The origins of these phases as well as their contributions to the adsorption process are discussed.