Chemostructurally Stable Polyionomer Coatings Regulate Proton-Intermediate Landscape in Acidic CO₂ Electrolysis.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Acidic media for CO2 electroreduction (CO2R) offer high carbon utilization but face challenges in achieving high selectivity and rates for multicarbon products due to proton and intermediate competition.
• Copper-based gas diffusion electrodes are benchmark catalysts for CO2R.

Purpose of the Study:

• To develop a strategy for modulating local proton and intermediate environments in acidic CO2R using a polyionomer coating.
• To improve the selectivity and efficiency of multicarbon (C2+) product formation during CO2R.

Main Methods:

• A polyionomer coating integrating amine (from PEI) and sulfonate/amphiphilic (from PFSA) functions was developed.
• The polyionomer coating was applied to copper gas diffusion electrodes.
• Performance was evaluated in a flow cell using 0.5 M K2/H2SO4 at pH 2 and a current density of 0.3 A cm-2.

Main Results:

• The polyionomer coating demonstrated H-bonding interactions and a stable structure-property relationship across a wide pH range (2-14).
• PFSA domains controlled *CO intermediates and the local ionic environment, while amines regulated proton availability and intermediate stabilization, enhancing C-C coupling.
• The optimized coating achieved a C2+ Faradaic efficiency of 61% and a single-pass CO2 utilization of 84%, with 64% conversion efficiency toward C2+ products.
• This represents a ~30% improvement in C2+ selectivity and a ~35% increase in carbon utilization compared to monofunctional coatings.

Conclusions:

• The polyionomer coating effectively modulates the CO2R microenvironment in acidic media, overcoming limitations of proton and intermediate competition.
• This approach significantly enhances the performance of copper-based electrodes for C2+ product formation.
• The findings provide a new strategy for designing advanced catalysts for efficient CO2 conversion.