Electron-Rich Subnanometer Cu Clusters Facilitate CO-CO Coupling in CO₂ Electroreduction

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• Subnanometer copper clusters on functional substrates show promise for electrochemical CO2 reduction (eCO2RR) to multicarbon products.
• The mechanistic basis for their enhanced C-C coupling activity is not well understood.

Purpose of the Study:

• To elucidate the electronic and structural factors governing CO-CO dimerization in g-C3N4-supported Cu8 clusters for eCO2RR.
• To understand how cluster properties influence CO adsorption, reactivity, and intermediate stabilization.

Main Methods:

• Machine learning-accelerated grand canonical Monte Carlo (ML-aGCMC) sampling.
• Grand canonical density functional theory (GC-DFT) calculations.
• Analysis of electronic structure, adsorption thermodynamics, and reaction barriers.

Main Results:

• Under negative potentials, CO adsorption is favored over formate, increasing C-C coupling likelihood.
• Cu8 clusters exhibit lower CO-CO coupling barriers than Cu(100) due to undercoordinated atoms and enhanced charge accumulation.
• Stabilization of the OCCO intermediate is achieved through strong electrostatic interactions driven by field-dipole coupling.

Conclusions:

• The electronic structure and cluster geometry of Cu8 are critical for mediating electron transfer and stabilizing intermediates in eCO2RR.
• Under operating conditions, CO-saturated Cu8(CO)15 species are dominant due to their population and kinetics.
• These findings provide design principles for improving valuable product formation in electrocatalysis.