Computational investigation of the adsorption of carbon dioxide onto zirconium oxide clusters

Abstract

A theoretical investigation of the adsorption of CO₂ onto ZrO₂ is presented. Various cluster models were used to mimic different basic and acidic sites on the surface. The method used was the density functional theory with the generalized gradient approximation and including Grimme's empirical model in order to properly describe the weak interactions that may occur between the adsorbate and the surface. We found that the adsorption at sites exhibiting two adjacent unsaturated zirconium atoms led to either the exothermic dissociation of CO₂ or to a strongly physisorbed state. By contrast, on a single unsaturated zirconium, CO₂ was adsorbed in an apical manner. In this case, the molecule is highly polarized and the adsorption energy amounts to -64.6 kJ mol⁻¹. Finally, the weakest adsorption of CO₂ occurred on the basic OH sites on the surface.