科研之友
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摘要
The adsorption of H-2 on the Cu2O(111) surface has been studied by spin-polarized density functional theory (DFT+U) calculations and atomic thermodynamics. It has been found that there exists reconstruction on a stoichiometric Cu2O(111) surface. The probability distribution of the reconstructed Cu2O(111) surfaces as a function of temperature has been analyzed using Boltzmann statistics. It has been found that the molecular H-2 prefers to adsorption on the uncoordinated Cu-CUS atom at low coverages (1/4 or 1/2 monolayer), while totally dissociative H-2 is preferred on the reconstructed Cu2O(111) surface at higher coverages (3/4 or 1 monolayer). For H-2 splitting on the Cu2O(111) surface, homolytical dissociative adsorption on two surface-uncoordinated Cu-CUS atoms is preferred which is a new mechanism for H-2 on metal oxides. More interesting is that the surface reconstruction will be recovered for eight hydrogen atoms binding on four uncoordinated Cu-CUS and four uncoordinated O-CUS atoms at saturation coverage. It has been found that the adsorbed H atoms will put out the lattice oxygen to the surface at higher coverage (five and six H-2), which agrees well with the experimental findings. The phase diagrams of H-2 binding on ideal and reconstructed Cu2O(111) surfaces were plotted and analyzed. In addition, we compared and analyzed the adsorption mechanisms of H-2 splitting on different metal oxides.
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