High-Coverage H₂ Adsorption on the Reconstructed Cu₂O(111) Surface

Abstract

The adsorption of H2 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 H2 prefers to adsorption on the uncoordinated CuCUS atom at low coverages (1/4 or 1/2 monolayer), while totally dissociative H2 is preferred on the reconstructed Cu2O­(111) surface at higher coverages (3/4 or 1 monolayer). For H2 splitting on the Cu2O­(111) surface, homolytical dissociative adsorption on two surface-uncoordinated CuCUS atoms is preferred which is a new mechanism for H2 on metal oxides. More interesting is that the surface reconstruction will be recovered for eight hydrogen atoms binding on four uncoordinated CuCUS and four uncoordinated OCUS 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 H2), which agrees well with the experimental findings. The phase diagrams of H2 binding on ideal and reconstructed Cu2O­(111) surfaces were plotted and analyzed. In addition, we compared and analyzed the adsorption mechanisms of H2 splitting on different metal oxides.

DFT Study of Azole Corrosion Inhibitors on Cu2O Model of Oxidized Copper Surfaces: I. Molecule–Surface and Cl–Surface Bonding

“…Bader analysis reveals that although H bonded to O sites is positively charged, it is not fully a proton-its Bader charge is about +0.6. In agreement with Yu et al [50], we also find that the Bader charge of H adsorbed to unsaturated Cu sites is significantly negative, being about −0.2 at Cu CUS and −0.3 at Cu Ovac and Cu Ovac Comparison of Mol * data presented in Figure 8 and H * data presented in Table 2 clearly reveals that, after the dissociation, the preferred co-adsorption structures consist of Mol * bonded to Cu sites and H * bonded to O sites; the latter thus forms an OH group at the surface. This is true even for Cu Ovac and Cu Ovac (110) sites, to which H * binds stronger than to O sites.…”

“…Notably, H binds the strongest to hollow site consisting of three adjacent Cu Ovac or Cu Ovac Table 2 summarizes the calculated adsorption data for H adsorbed at various sites on Cu 2 O surfaces, whereas the corresponding structures are depicted in Figure 13. Our calculated H-O and H-Cu bond lengths are in good agreement with those reported in the literature [23,50]. Bader analysis reveals that although H bonded to O sites is positively charged, it is not fully a proton-its Bader charge is about +0.6.…”

“…It seems intuitive to assume that H * bonds to O surface sites. Calculations indeed confirm this anticipation; however, they also reveal that H can bond strongly to unsaturated Cu ions (Table 2), in agreement with previous studies [23,50]. Notably, H binds the strongest to hollow site consisting of three adjacent Cu Ovac or Cu Ovac Table 2 summarizes the calculated adsorption data for H adsorbed at various sites on Cu 2 O surfaces, whereas the corresponding structures are depicted in Figure 13.…”

DFT-Based Cu(111)||Cu2O(111) Model for Copper Metal Covered by Ultrathin Copper Oxide: Structure, Electronic Properties, and Reactivity

“…It is known that the Cu 2 O(111) surface reconstructs after cleavage of the bulk structure. 18,20,60,61 There are three symmetry equivalent directions along which Cu cus ions may relax, with slightly different relaxation energies. 60 The relaxation of the surface was also attested by the surface interlayer distance variation, shown in Figure 5 and calculated by the following equation:…”

Interface atom mobility and charge transfer effects on CuO and Cu2O formation on Cu3Pd(111) and Cu3Pt(111)

“… and CuO, two of the most common forms of Cu oxides, find applications as anodes in lithium ion battery 4 and solar cells 5 . Copper oxides are also expected to be used as catalysts for CO 6 , NO dissociation 7 , adsorption of 8 , 9 – 11 , and 12 , 13 . Similarly, the catalytic reactivities of Cu oxides vary with the Cu oxidation state.…”