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With quantum-chemical calculations, we investigated the hydrogenation of a CO2 molecule on Fe(111) and W(111) surfaces using the density functional theory (DFT) with the projector-augmented wave (PAW) approach in periodic boundary condition. The structures and geometric parameters of the hydrogenation products, and the potential-energy surfaces, were calculated. It was shown that similar reaction paths for the hydrogenation of CO2 on Fe(111) and W(111) surfaces were found but with disparate energies. The rate-controlling energy barriers from M-CO2 (M = Fe, W) plus H atom to form formate (HCOO) and carboxyl (COOH) on a Fe(111) surface are 0.37 and 1.69 eV, respectively, but 0.54 and 2.79 eV, respectively, on a W(111) surface. The most probable path for the hydrogenation of a CO2 molecule on either the Fe(111) or W(111) surface is the formation of a formate-vertical structure. To understand the interaction between adsorbates and surfaces, we calculated the Bader charges and analyzed the local densities of states.

Using density-functional theory (DFT), we investigated the oxidation of CO on Au 55 , Ag 13 Au 42 , Au 13 Ag 42 , and Ag 55 metal clusters of nm size. The structures of oxidation intermediates and at the transition states on the potential-energy surfaces were derived with the nudged-elastic-band (NEB) method. According to our results, the coupling of CO and O 2 molecules to form intermediate OCOO has the least energy barrier (0.13 eV) on the Ag 13 Au 42 core−shell nanocluster, whereas the dissociation of the O− O bond of OCOO to form CO 2 and O on the Au 13 Ag 42 core−shell nanocluster is the easiest process with a 0.15 eV barrier height. To understand the electronic property of these nanocluster catalysts and their interactions with the adsorbates, we calculated the electron localization functions, Bader charges, and local densities of states; the results were consistent and explicable.

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