A unifying mechanism for cation effect modulating C1 and C2 productions from CO₂ electroreduction

Area of Science:

• Surface Science
• Electrocatalysis
• Computational Chemistry

Background:

• Electrocatalysis is governed by electron transfer across the electric double layer at the catalyst-electrolyte interface.
• The CO2 reduction reaction's rate strongly depends on alkali metal cation identity, yet a molecular understanding is lacking.
• Understanding the electric double layer structure's role in electron transfer is crucial for optimizing electrocatalytic processes.

Purpose of the Study:

• To elucidate the molecular mechanisms linking alkali metal cations and electrocatalytic CO2 reduction.
• To establish the role of cation-electrolyte interactions in electron transfer (ET) pathways.
• To rationalize the performance enhancement observed with Nafion-coated electrodes for C2 production.

Main Methods:

• Quantum-mechanics-based atom-scale simulations were employed to investigate cation-coupling with reaction intermediates.
• Theoretical models were developed to describe H+ and M+-associated electron transfer mechanisms.
• Experimental validation involved analyzing Nernstian shifts in polarization curves and reaction kinetics.

Main Results:

• Distinct H+- and M+-associated electron transfer mechanisms were established for methane and CO/C2H4 formation, respectively.
• Simulation results were corroborated by experimental data showing concentration-dependent Nernstian shifts and first-order kinetics.
• Enhanced surface charge density on Nafion-coated electrodes was identified as key to improved C2 production.

Conclusions:

• The study provides a unified molecular picture of alkali metal cation effects in CO2 electroreduction.
• Electron transfer mechanisms are directly linked to the electric double layer structure and cation interactions.
• Nafion-coated electrodes enhance C2 production by increasing surface charge density, optimizing cation influence.