Adsorption and dissociation of O 2 on the Cu 2O(1 1 1) surface: Thermochemistry, reaction barrier

Abstract

The adsorption and dissociation of O 2 on the perfect and oxygen-deficient Cu 2O(1 1 1) surface have been systematically studied using periodic density functional calculations. Different kinds of possible modes of atomic O and molecular O 2 adsorbed on the Cu 2O(1 1 1) surface are identified: atomic O is found to prefer threefold 3Cu site on the perfect surface and O vacancy site on the deficient surface, respectively. Cu CUS is the most advantageous site with molecularly adsorbed O 2 lying flatly over singly coordinate Cu CUS–Cu CSA bridge on the perfect surface. O 2 adsorbed dissociatively on the deficient surface, which is the main dissociation pathway of O 2, and a small quantity of molecularly adsorbed O 2 has been obtained. Further, possible dissociation pathways of molecularly adsorbed O 2 on the Cu 2O(1 1 1) surface are explored, the reaction energies and relevant barriers show that a small quantity of molecularly adsorbed O 2 dissociation into two O atoms on the deficient surface is favorable both thermodynamically and kinetically in comparison with the dissociation of O 2 on the perfect surface. The calculated results suggest that the presence of oxygen vacancy exhibits a strong chemical reactivity towards the dissociation of O 2 and can obviously improve the catalytic activity of Cu 2O, which is in agreement with the experimental observation.