Fast Transformation of CO₂ into CO Via a Hydrogen Bond Network on the Cu Electrocatalysts

Abstract

In the present study, we have performed ab initio molecular dynamics (AIMD) simulations combined with an explicit solvent model to probe the mechanism of CO2 electroreduction to CO on a copper catalyst. In the presence of an explicit water environment, we have identified an anisotropic adsorption of CO2 at the copper–water interface where one C–O bond penetrates to the solvent and the other one is parallel to the surface. This type of titled configuration suggests a competitive interaction between the copper catalyst and the solvent toward CO2 adsorption, therefore leading to the activation of CO2. It is further found that the C–O bond in the solvent is easier to hydrogenate because of the formation of hydrogen bonds, while the C–O bond parallel to the surface is much more elongated (i.e., activated) due to the efficient charge transfer from copper. Although the hydrogenation is calculated to be favorable at the C–O bond in the solvent, the MD simulations suggest a fast-irreversible proton transformation from the C–O bond in the solvent to the C–O bond on the surface via the hydrogen bond network. This process finally results in the formation of COOH species on the copper surface, accounting for the low kinetic barrier for CO formation. Our work properly rationalizes the experimental observations of CO2RR on the copper surface, which provides a fundamental understanding of the fast formation of CO* from CO2 on the Cu(100) surface at a less negative overpotential.