# Spatially Resolved Differentiation of Functional Degradation and Perforating Structural Defects in Membrane Electrode Assemblies Using Diffusion-Cell Coupled DC-SECM

## TL;DR

This paper introduces a new method to detect and differentiate membrane damage in fuel cells using electrochemical microscopy.

## Contribution

A novel spatially resolved method combining SECM and a diffusion cell to distinguish functional and structural membrane degradation.

## Key findings

- SECM scans at cathodic potential measure proton conductivity through the membrane.
- SECM scans at anodic potential visualize structural defects like cracks and holes.
- The method was validated on pristine and aged membranes in real fuel cell conditions.

## Abstract

In order to increase the lifetime of polymer electrolyte
membrane
(PEM) fuel cells (PEMFCs) and water electrolyzers (PEMWEs), understanding
local degeneration processes in membrane electrode assemblies (MEAs)
is crucial. By a combination of scanning electrochemical microscopy
(SECM) with a flow-through diffusion cell (DiffC-DC-SECM) and ferrocyanide
and protons as redox mediators, a spatially resolved analytical method
was developed that can differentiate between different functional
and structural degeneration phenomena in the aging process of a membrane.
An SECM scan at cathodic potential detects the diffusion of protons
through the membrane and thus its through-plane proton conductivity,
while a second SECM scan at anodic potential visualizes the diffusion
of the iron complex through the membrane, thus perforating structural
damage such as cracks and holes. The method was successfully validated
for the spatially resolved differentiation of membrane damage in pristine
PEMs and catalyst-coated membranes (CCMs) with artificial holes, chemically
aged CCMs, and MEAs in fully assembled operational PEMFCs aged by
an open-circuit voltage membrane accelerated stress test. DiffC-DC-SECM
thus provides a powerful technique with high local resolution for
membrane integrity testing under realistic operation conditions to
develop long-term durable materials for PEMFCs and PEMWEs.