Specific Adsorption of Alkaline Cations Enhances CO-CO Coupling in CO₂ Electroreduction

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Electrolyte cations influence electrochemical CO2 reduction (eCO2R) selectivity for multicarbon products.
• The mechanism of cation effects on C-C coupling in eCO2R is not fully understood.

Purpose of the Study:

• Investigate the role of potassium ions (K+) in the C-C coupling mechanism during eCO2R on copper surfaces.
• Elucidate the origin of the cation effect on reaction selectivity.

Main Methods:

• Constant-potential ab initio molecular dynamics (AIMD) simulations.
• Electronic structure analysis.
• Experimental validation using cetyltrimethylammonium bromide (CTAB).

Main Results:

• K+ specifically adsorbs near *CO intermediates on Cu surfaces, enhancing C-C coupling kinetics.
• Specific K+ adsorption reduces coupling barriers by ~0.20 eV via charge redistribution.
• Cu(100) with K+ shows high *CO-*CO coupling selectivity.
• Experimental suppression of K+ adsorption drastically lowers C2 product selectivity.

Conclusions:

• Specific K+ adsorption is crucial for enhancing C-C coupling and C2+ product selectivity in eCO2R.
• Tuning interfacial cation adsorption offers a strategy to improve eCO2R efficiency.
• Promoting K+ specific adsorption, e.g., via confinement or pulsed potentials, can enhance C-C coupling.