Operando Raman Spectroscopy Reveals Degradation Byproducts from Ionomer Oxidation in Anion Exchange Membrane Water...

Area of Science:

• Electrochemistry
• Materials Science
• Spectroscopy

Background:

• Anion exchange membrane water electrolyzers (AEMWE) offer a promising alternative to traditional electrolyzers.
• Understanding catalyst and ionomer degradation is crucial for AEMWE long-term stability.
• Non-platinum group metal (PGM-free) catalysts are being explored to reduce cost.

Purpose of the Study:

• To investigate the degradation mechanisms of PGM-free catalysts and ionomers in AEMWE.
• To identify breakdown products generated under high oxidative potential conditions.
• To correlate degradation pathways with specific operational parameters.

Main Methods:

• Development of a unique, customized test cell for potentiostatic operation.
• Utilized operando Raman spectroscopy to monitor degradation in situ.
• Designed and fabricated 3D-printable flow cells for spatially resolved measurements.

Main Results:

• Identified degradation products from hydroxide-conductive polymer ionomers and membranes.
• Detected Raman signals corresponding to carboxylic and aromatic functional groups.
• These signals indicate the presence of small molecule breakdown products in the electrolyte.

Conclusions:

• Proposed a multistep, free radical reaction pathway as the origin of ionomer/membrane degradation.
• Demonstrated that chain scission of the poly aryl backbone occurs.
• Operando Raman spectroscopy is effective for elucidating degradation mechanisms in AEMWE.