Initial Reduction of CO2 on Pd-, Ru-, and Cu-Doped CeO2(111) Surfaces: Effects of Surface Modification on Catalytic Activity and Selectivity

Abstract

Surface modification by metal doping is an effective treatment technique for improving surface properties for CO₂ reduction. Herein, the effects of doped Pd, Ru, and Cu on the adsorption, activation, and reduction selectivity of CO₂ on CeO₂(111) were investigated by periodic density functional theory. The doped metals distorted the configuration of a perfect CeO₂(111) by weakening the adjacent Ce-O bond strength, and Pd doping was beneficial for generating a highly active O vacancy. The analyses of adsorption energy, charge density difference, and density of states confirmed that the doped metals were conducive for enhancing CO₂ adsorption, especially for Cu/CeO₂(111). The initial reductive dissociation CO₂ → CO* + O* on metal-doped CeO₂(111) followed the sequence of Cu- > perfect > Pd- > Ru-doped CeO₂(111); the reductive hydrogenation CO₂ + H → COOH* followed the sequence of Cu- > perfect > Ru- > Pd-doped CeO₂(111), in which the most competitive route on Cu/CeO₂(111) was exothermic by 0.52 eV with an energy barrier of 0.16 eV; the reductive hydrogenation CO₂ + H → HCOO* followed the sequence of Ru- > perfect > Pd-doped CeO₂(111). Energy barrier decomposition analyses were performed to identify the governing factors of bond activation and scission along the initial CO₂ reduction routes. Results of this study provided deep insights into the effect of surface modification on the initial reduction mechanisms of CO₂ on metal-doped CeO₂(111) surfaces.

Keywords: CO2 reduction; density functional theory; energy barrier decomposition; metal-doped CeO2(111); selectivity.