Mercaptoimidazole-Engineered Microenvironment Enables Durable CO₂ Electroreduction in a Zero-Gap PEM Electrolyzer.

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Proton exchange membrane (PEM) electrolysis offers sustainable CO2 conversion but struggles with balancing hydrogen evolution suppression and salt precipitation.
• Existing catalysts face challenges in maintaining high selectivity and stability under demanding operating conditions.

Purpose of the Study:

• To resolve the trade-off in CO2 conversion electrolysis by developing a catalyst that prevents carbonate formation while suppressing side reactions.
• To engineer a catalyst with a tailored microenvironment for enhanced CO2 reduction performance in PEM electrolyzers.

Main Methods:

• Molecular-level engineering of a lead-based catalyst by anchoring a mercaptoimidazole ligand.
• Utilizing operando spectroscopic analyses and theoretical studies to understand catalyst surface phenomena.
• Integrating the engineered catalyst into a zero-gap PEM electrolyzer for performance evaluation.

Main Results:

• The mercaptoimidazole ligand created an alkaline microenvironment and proton-shielding effect at the catalyst surface.
• Achieved a peak formate Faradaic efficiency of 95.8% and sustained >90% selectivity at 600 mA cm⁻².
• Demonstrated stable operation (>300 h) under acidic (pH 1.0) and cation-starved conditions.

Conclusions:

• The developed catalyst design decouples the catalytic microenvironment from the bulk electrolyte, overcoming previous limitations.
• This strategy enables durable and highly selective acidic CO2 electrolysis, paving the way for efficient chemical production.
• The findings provide a new design principle for advanced electrochemical CO2 conversion systems.