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

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.