Solvent-mediated outer-sphere CO₂ electro-reduction mechanism over the Ag111 surface

Area of Science:

• Electrochemistry
• Catalysis
• Computational Chemistry

Background:

• Electrocatalytic CO2 reduction (CO2RR) is vital for clean energy.
• Understanding CO2RR mechanisms is crucial for designing efficient electrodes.
• Electrolyte composition and electrical double layer (EDL) influence CO2RR.

Purpose of the Study:

• Investigate the role of the EDL in CO2 activation and conversion.
• Elucidate CO2RR mechanisms at high cathodic bias on a silver surface.
• Identify pathways for CO2 reduction influenced by the EDL.

Main Methods:

• Multiscale modeling approach.
• Density Functional Theory (DFT) calculations.
• Ab initio molecular dynamics simulations.

Main Results:

• A dense EDL hinders CO2 diffusion to the catalyst surface.
• Favorable CO2 reduction pathways occur directly over the EDL.
• An outer-sphere mechanism promotes formate formation.
• Solvated alkali cations in the EDL stabilize CO to CO conversion.

Conclusions:

• The EDL plays a critical, non-innocent role in CO2RR.
• Outer-sphere reduction in the EDL favors formate production.
• EDL properties can be tuned to optimize CO2RR selectivity and efficiency.