Competitive adsorption of CO₂ and H₂O molecules on the BaO (100) surface: A first-principle study

CO₂ adsorption on mineral sorbents has a potential to sequester CO₂. This study used a density functional theory (DFT) study of CO₂ adsorption on barium oxide (BaO) in the presence of H ₂O to determine the role of H₂O on the CO₂ adsorption properties on the (2 × 2; 11.05 Å × 11.05 Å) BaO (100) surface because BaO shows a high reactivity for CO₂ adsorption and the gas mixture of power plants generally contains CO₂ and H₂O. We investigated the adsorption properties (e.g., adsorption energies and geometries) of a single CO₂ molecule, a single H ₂O molecule on the surface to achieve molecular structures and molecular reaction mechanisms. In order to evaluate the coordinative effect of H₂O molecules, this study also carried out the adsorption of a pair of H₂O molecules, which was strongly bounded to neighboring (-1.91 eV) oxygen sites and distant sites (-1.86 eV), and two molecules (CO₂ and H₂O), which were also firmly bounded to neighboring sites (-2.32 eV) and distant sites (-2.23 eV). The quantum mechanical calculations show that H₂O molecule does not influence on the chemisorption of CO ₂ on the BaO surface, producing a stable carbonate due to the strong interaction between the CO₂ molecule and the BaO surface, resulting from the high charge transfer (-0.76 e).