Probing Interfaces in Membrane Electrode Assemblies via Operando Infrared Spectroscopy at Model Gas-Liquid-Solid...

Area of Science:

• Electrochemistry
• Spectroscopy
• Materials Science

Background:

• Understanding the triple-phase boundary (TPB) is critical for efficient CO2 electroreduction in membrane electrode assemblies (MEAs).
• Direct probing of the buried catalyst-membrane interface during high-rate operation remains a significant challenge.

Purpose of the Study:

• To develop and demonstrate an operando surface-enhanced infrared absorption spectroscopy (SEIRAS) platform for investigating the TPB in MEAs.
• To gain molecular-level insights into adsorbate and hydration dynamics at the catalyst-membrane interface during CO2 electroreduction.

Main Methods:

• Development of an MEA-type SEIRAS platform enabling operando measurements.
• Utilizing Cu deposited-Au film and sputtered Cu film substrates for CO2 electroreduction.
• Employing SEIRAS to selectively detect the buried catalyst-membrane interface at high current densities (up to 247 mA/cm2).

Main Results:

• CO adsorption was observed to persist and reach near-saturation coverage at the TPB even at high current densities.
• Preferential depletion of cation-coordinated water was detected.
• CO2 reduction led to carbonate formation, altering the water hydrogen-bonding network to an ice-like structure.

Conclusions:

• Operando MEA-SEIRAS provides molecular-level evidence of adsorbate and hydration dynamics at the TPB.
• The developed platform is a general approach for probing buried electrochemical interfaces during catalysis.
• Findings offer insights into reaction mechanisms and catalyst stability in MEAs for CO2 electroreduction.