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)–CuCUS 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 CuCUS 3d and CuCUS 4s of stoichiometric O-terminated Cu2O (1 1 1) surface. These results showed that H2 molecule adsorption on CuCUS 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 CuCSA, OCUS and OCSA atoms and the H2 molecule is only very weakly bound to the Cu2O (1 1 1)–CuCUS surface. From the analysis of stoichiometric O-terminated Cu2O (1 1 1) Local Density of States, it is observed that CuCUS 3d orbital has moved to a lower energy and the sharp band of CuCUS 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 CuCUS site showed that H2 molecule obtained electron from CuCUS which was consistent with the calculated electronic structural changes upon H2 adsorption.