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We investigated the adsorption of CO on the flat, stepped, and kinked copper surfaces from density functional theory calculations as well as the temperature programmed desorption and X-ray photoelectron spectroscopy. Several exchange-correlation functionals have been considered to characterize CO adsorption on the copper surfaces. We used the van der Waals density functionals (vdW-DFs), i.e., the original vdW-DF (vdW-DF1), optB86b-vdW, and rev-vdW-DF2, as well as the Perdew-Burke-Ernzerhof (PBE) with dispersion correction (PBE-D2). We have found that vdW-DF1 and rev-vdW-DF2 functionals slightly underestimate the adsorption energy, while PBE-D2 and optB86b-vdW functionals give better agreement with the experimental estimation for CO on Cu(111). The calculated CO adsorption energies on the flat, stepped, and kinked Cu surfaces are 20-27 kJ/mol, which are compatible with the general notion of physisorbed species on solid surfaces. Our results provide a useful insight into appropriate vdW functionals for further investigation of related CO activation on Cu surfaces such as methanol synthesis and higher alcohol production.

We studied the dissociative adsorption of CO2 to CO + O on the Cu(111), Cu(221), Cu(211), and Cu(11 5 9) surfaces by using state-of-the-art density functional theory (DFT) within a generalized gradient approximation (GGA) and van der Waals density functional (vdW-DF) calculations. The activation energy for CO2 dissociation on the flat Cu(111) surface is 1.33 eV. The activation energies on stepped and kinked surfaces are 1.06 eV, 0.67 eV, and 1.02 eV for the Cu(221), Cu(211), and Cu(11 5 9) surfaces, respectively. Even though the activation energy is 0.66 eV lower on the stepped Cu(211) surface than on the flat Cu(111) surface, we conclude that CO2 does not dissociate on "ideal" flat, stepped, or kinked Cu surfaces at low temperature. We attribute the discrepancy between our theoretical results and experimentally observed CO2 dissociation on stepped Cu surfaces below 150 K to other factors such as effects of Cu adatoms, gas phase or condensed CO2 molecules, or interaction with other gas phase molecules.

We performed ab initio molecular dynamics analysis of formate decomposition to CO and H on a Cu(111) surface using van der Waals density functionals. Our analysis shows that the desorbed CO has approximately twice larger bending vibrational energy than the translational, rotational, and stretching vibrational energies. Since formate synthesis, the reverse reaction of formate decomposition, has been suggested experimentally to occur via the Eley-Rideal mechanism, our results indicate that the formate synthesis can be enhanced if the bending vibrational mode of CO is excited rather than the translational and/or stretching vibrational modes. Detailed information on the energy distribution of desorbed CO as a formate decomposition product may provide new insights for improving the catalytic activity of formate synthesis.