Ionomer Structure Engineering for Optimal Triple-Phase Boundaries in Anion Exchange Membrane Water Electrolysers

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Anion exchange membrane water electrolyzers (AEMWEs) require efficient triple-phase boundaries (TPBs) for optimal performance.
• Catalyst agglomeration and ionomer distribution in catalyst layers (CLs) hinder TPB formation, especially with metal oxide catalysts.

Purpose of the Study:

• To investigate how the chemical structure of anion exchange ionomers (AEIs) influences catalyst agglomerate dispersion and ionomer penetration within CLs.
• To correlate AEI structure with CL morphology and AEMWE performance.

Main Methods:

• Systematic evaluation of three commercial AEIs (PiperION A5, Sustainion XA-9, Fumion FAA-3) in AEMWEs.
• Analysis of CL morphology and electrochemical performance.
• Engineering of novel AEIs with tailored flexibility and swelling properties.

Main Results:

• Flexible, hydrophilic AEIs promote better penetration into catalyst aggregates, forming internal binding networks and enhancing active-site exposure.
• Reduced ionomer content further optimizes TPB construction and improves AEMWE performance.
• Engineered aryl piperidinium ionomers with meta-terphenyl and triphenylbenzene modifications achieved 1.60 V at 1 A cm⁻².

Conclusions:

• AEI chemical structure is critical for CL morphology and TPB formation in AEMWEs.
• Flexible ionomers are key to minimizing film-like coverage and charge-transfer resistance.
• Design principles for next-generation anodic AEIs can be derived from understanding AEI structure-property relationships.