Adsorption of CO₂ on Model Surfaces of Cesium Oxides Determined from First Principles

Gradient-corrected periodic density functional theory was used to examine the bulk and low index surfaces of several cesium oxides (Cs₂O, Cs₂O₂, and CsO₂). The adsorption of CO₂ on those surfaces was explored. The cesium-terminated {001} surface of Cs₂O had a weak affinity for CO₂ with an adsorption strength of only −4.1 kJ mol^-1. In contrast, the Cs₂O {010} surface exposing both Cs and O atoms adsorbed CO₂ with a strength of −284 kJ mol^-1. The adsorption of CO₂ in the bridged configuration on the {001} and the {100} surfaces of Cs₂O₂ exhibited adsorption strengths of −101 and −186 kJ mol^-1, respectively. The oxygen-rich CsO₂ surface failed to adsorb CO₂. Results from a Mulliken charge analysis are consistent with the traditional ranking of basicity:  Cs₂O > Cs₂O₂ > CsO₂.