Operando Spectroscopic Insights into CO₂ Reduction at Electrode/Polyelectrolyte Interfaces

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• The electrode/polyelectrolyte interface in membrane electrode assembly (MEA) configurations is critical for electrochemical technologies but poorly understood.
• Investigating interfacial structure and catalytic behavior is essential for improving MEA performance.

Purpose of the Study:

• To elucidate the CO2 reduction mechanism at the electrode/polyelectrolyte interface in a practical MEA electrolyzer.
• To provide direct spectroscopic evidence of key reaction intermediates.

Main Methods:

• Developed an integrated operando Raman spectroscopy and mass spectrometry (MS) method.
• Utilized isotope labeling experiments and ab initio molecular dynamics (AIMD) simulations.
• Operated a practical MEA electrolyzer at high current densities.

Main Results:

• Provided the first direct spectroscopic evidence of the *CCO intermediate, crucial for C2 product formation.
• Observed the absence of the linearly adsorbed *CO_L intermediate, typically seen in liquid electrolytes.
• Identified a shift in the rate-determining step to *CCO hydrogenation.

Conclusions:

• The unique electrode/polyelectrolyte interface structure influences CO2 reduction pathways.
• Understanding these interfacial characteristics is key to advancing CO2 MEA electrolyzer performance.
• This work offers insights for designing more efficient CO2 conversion systems.