Molecular and dissociative O2 adsorption on the Cu2O(111) surface.

The adsorption of O2 on the Cu2O(111) surface at different coverages has been studied by spin-polarized density functional theory (DFT+U) calculations and atomic thermodynamics. It has been found that the dissociative O2 prefers to adsorb on the reconstructed Cu2O(111) surface at low coverages (1/4 to 1 monolayer), while totally dissociative and mixed molecular and dissociative O2 prefers to adsorb on the reconstructed Cu2O(111) surface thermodynamically at higher coverages (5/4 to 7/4 monolayers). More interesting is that the CuO film can be automatically formed on the Cu2O(111) surface that was induced by the surface reconstruction of the Cu2O(111) surface and adsorption of four dissociative O2 molecules (1 monolayer), which agrees well with the recent experimental results. Along higher coverages of O2 adsorption (5/4 to 7/4 monolayers), much stronger surface reconstruction and relaxation was found. The probability distribution of different single-O2 adsorbed states on the Cu2O(111) surface as a function of temperature was analyzed using a Boltzmann model. The adsorption mechanism of O2 on the Cu2O(111) surface was analyzed using the phase diagram and compared with other metal oxides.