Insights into Nonelectroactive C-C Bond Formation on Cu(100) during Electrochemical CO₂ Reduction from...

Area of Science:

• Electrochemistry
• Surface Science
• Computational Chemistry

Background:

• Carbon-carbon bond formation is key for synthesizing hydrocarbons via electrochemical CO and CO2 reduction.
• Copper (Cu) is known for its ability to produce hydrocarbons, particularly ethylene on its (100) facet.
• Previous simulations suggested C-C bond formation is kinetically controlled in early reduction stages.

Purpose of the Study:

• To investigate the mechanisms of carbon-carbon bond formation during electrochemical CO and CO2 reduction on Cu(100).
• To re-evaluate previous density functional theory (DFT) predictions using more accurate many-body wavefunction theory.
• To understand the role of adsorbed CO and its intermediates in C-C coupling.

Main Methods:

• Simulations using correlated wavefunction theory with an embedding scheme.
• Calculation of free energy barriers for C-C bond formation pathways.
• Analysis of reaction kinetics and surface mobility of intermediates.

Main Results:

• Coupling of adsorbed CO with another CO or COH is highly kinetically impeded (>1 eV barrier), contradicting DFT predictions.
• Coupling of two adsorbed COH intermediates is energetically favorable (<0.3 eV barrier, exoergic).
• Low surface mobility of COH makes its dimerization improbable at low coverages.

Conclusions:

• Nonelectroactive C-C bond formation involving CO is unlikely on pristine Cu(100).
• The prevailing hypothesis of kinetically determined C2 product emergence needs revision.
• COH dimerization may become significant only at high COH surface coverages.