科研之友
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摘要
Interaction of atomic and molecular oxygen with perfect and defective Cu2O (111) surfaces has been studied by periodic density functional theory coupled with slab models. Different kinds of possible modes of O and O-2 adsorbed on Cu2O (111) surface and possible dissociation pathways were calculated. Meanwhile, different electronic states, i.e., the singlet and the triplet states were considered in the computation. The optimization of the geometry, calculation of the adsorption energy, vibrational frequency and analysis of the Mulliken population were carried out. The results indicate that Cu-CSA site is slightly more favorable than Cu-CUS for O adsorption, and for O-2 adsorption over perfect surface, Cu-CUS site is the most advantageous position, especially for O-2 with end-on type. For O-2 adsorption over the deficient surface, it has a larger adsorption energy compared to O2 adsorption over the perfect surface and the O-O bond strength is considerably weakened when O-2 lies flatly on the oxygen vacancy site and lies flatly over 1-vacancy bridge site. And the oxygen adspecies is characteristic of a classical O-2(-) ion on perfect surface, whereas is O-2(2-) ion on oxygen-deficient surface. The calculations for transition states show that the dissociation reaction of O-2 on deficient surface is highly exothermic with a very small barrier height.
