Density functional theory calculations of surface properties and H2 adsorption on the Cu2O (1 1 1) surface

First-principles calculation on the basis of the density functional theory (DFT) and generalized gradient approximation have been applied to study the adsorption of H₂ on the stoichiometric O-terminated Cu₂O (1 1 1), Cu₂O (1 1 1)-Cu_CUS and Cu-terminated Cu₂O (1 1 1) surfaces. The optimal adsorption position and orientation of H₂ on the stoichiometric O-terminated Cu₂O (1 1 1) surface and Cu-terminated Cu₂O (1 1 1) surface were determined and electronic structural changes upon adsorption were investigated by calculating the Local Density of States (LDOS) of the Cu_CUS 3d and Cu_CUS 4s of stoichiometric O-terminated Cu₂O (1 1 1) surface. These results showed that H₂ molecule adsorption on Cu_CUS site parallel to stoichiometric O-terminated Cu₂O (1 1 1) surface and H₂ molecule adsorption on Cu₂ site parallel to Cu-terminated Cu₂O (1 1 1) surface were the most favored, respectively. The presence of surface copper vacancy has a little influence on the structures when H₂ molecule adsorbs on Cu_CSA, O_CUS and O_CSA atoms and the H₂ molecule is only very weakly bound to the Cu₂O (1 1 1)-Cu_CUS surface. From the analysis of stoichiometric O-terminated Cu₂O (1 1 1) Local Density of States, it is observed that Cu_CUS 3d orbital has moved to a lower energy and the sharp band of Cu_CUS 4s is delocalized when compared to that before H₂ molecule adsorption, and overlapped substantially with bands due to adsorbed H₂ molecule. The Mulliken charges of H₂ adsorption on Cu_CUS site showed that H₂ molecule obtained electron from Cu_CUS which was consistent with the calculated electronic structural changes upon H₂ adsorption.