First-principles investigation of methanol synthesis from CO2 hydrogenation on Cu@Pd core–shell surface

In this paper, the density functional theory calculation is used to investigate the reaction mechanisms of CO2 hydrogenation to CH3OH on the Cu@Pd core–shell surface. In particular, the possible adsorption sites, structural parameters, and adsorption energies of all intermediates are determined. All the reaction energies and the activation barriers of elementary steps involved in the possible hydrogenation mechanisms, including the HCOO pathway, the COOH pathway, and the RWGS + CO-Hydro pathway, are studied in detail. The calculated activation barrier of the rate-determining step is 1.84 eV for the HCOO pathway, 1.45 eV for the COOH pathway, and 1.17 eV for the RWGS + CO-Hydro pathway. Therefore, the most favorable hydrogenation mechanism on the Cu@Pd core–shell surface is following the reverse water–gas shift reaction followed by CO hydrogenation and will be completed via the route of CO2* → trans-COOH* → cis-COOH* → CO* → HCO* → HCOH* → H2COH* → CH3OH*. Compared with Cu-based catalysts such as Cu(111), Cu29 cluster, Cu19 cluster, and Cu(211), the Cu@Pd core–shell catalyst is demonstrated to have higher catalytic activity toward CO2 hydrogenation to CH3OH.