CO₂ adsorption on H₂O-saturated BaO(1 0 0) and induced barium surface dissociation

CO₂ adsorption on a barium oxide (BaO) surface saturated with a monolayer of H₂O molecules was studied; a monolayer of H₂Omolecules on the BaO surface exhibits nondissociative or dissociative adsorption. During the nondissociative reaction, a hydroxyl ion-terminated surface is produced, resulting in the formation of barium hydroxide (Ba(OH) ₂) on the surface. The Ba(OH)₂ from the substrate associates with the tightly bound CO₂ molecule, resulting in the formation of barium carbonate (BaCO₃). In contrast, during the dissociative H₂O adsorption, a hydrogen-terminated surface is produced, which strongly adsorbs CO₂ molecules. The H₂O molecules on a fully saturated BaO surface (containing multiple layers of H₂O molecules) readily aggregate, and Ba dissociation takes place on the hydrated surface, possibly resulting in a surface containing Ba defects.