Challenges and Opportunities in Understanding Proton Exchange Membrane Fuel Cell Materials Degradation Using In‐Situ Electrochemical Liquid Cell Transmission Electron Microscopy

Abstract

Environmental pollution at the current state of fossil fuel consumption has led clean energy devices like proton exchange membrane fuel cells (PEMFCs) to emerge as alternative energy generation solutions. However, the performance, durability, and efficiency limitations of PEMFCs have hindered their widespread adoption. Improving their performance and durability can be achieved by fundamentally understanding and tuning their catalyst layer structures and compositions. Transmission electron microscopy and scanning transmission electron microscopy have proven to be among the best characterization tools available to analyze the microstructural features of the catalyst layers of PEMFC devices. The ability to directly observe changes in catalyst materials during operation with high spatial and temporal resolutions by the means of In‐situ techniques can accelerate material development in the PEMFC field. In this article, structure, properties, and performance of PEMFC materials are reviewed, and their known degradation mechanisms are introduced. Available In‐situ TEM techniques are presented to guide the selection of suitable methods and approaches for studying the PEMFC systems. Finally, the current literature is presented on PEMFC research that has used In‐situ electrochemical liquid cell TEM to study materials evolution and degradation, highlighting the specific challenges and opportunities for applying the technique in the PEMFCs’ field.

Double-Layer Expanded Polytetrafluoroethylene Reinforced Membranes with Cerium Oxide Radical Scavengers for Highly Stable Proton Exchange Membrane Fuel Cells

“…With low pollution, low noise, and high efficiency, proton exchange membrane fuel cells (PEMFCs) are considered a promising green energy technology. − Nevertheless, due to the restriction of some technical barriers, their promotion and application are unsatisfactory. Thereinto, the inferior service life of the PEMFCs is a significant obstacle.…”

“…In particular, the PFSA membranes possess a large fluctuation in swelling rate (i.e., poor dimensional stability) under changing humidity conditions. The mechanical failure can induce reactant crossover and the deterioration of the membrane–catalyst interface and eventually reduce the lifespan of PEMFCs. ,,, In contrast, their chemical degradation behaviors are predominantly reflected by the thinning, cracks, and pinholes of membranes caused by the decomposition of PFSA ionomers. In practice, PEMs are exposed to an oxidizing environment composed of hydroxyl (HO*), hydroperoxyl (HOO*), and hydrogen peroxide (H 2 O 2 ).…”

An Epoxy‐Free Sample Preparation Approach to Enable Imaging of Ionomer and Carbon in Polymer Electrolyte Membrane Fuel Cells

“…[ 5,6 ] Pt degradation can proceed through different mechanisms, i.e., Pt dissolution/precipitation, Ostwald ripening, Pt migration, Pt detachment, and Pt poisoning, that have been long considered as the main degradation mechanisms of the catalyst. [ 7 ] The degradation of Pt, exhibited as an increase in the size of particles, can occur in both anode and cathode electrodes. [ 8 ] All different cathode Pt catalyst degradation mechanisms are possible under different operating conditions.…”

Mechanistic interactions in polymer electrolyte fuel cell catalyst layer degradation

“…The degradation mechanisms that occur in an operating environment along with their challenges, opportunities, and material evolution have been summarized in recent review articles. [10][11][12][13] Under the application of a durability protocol, the impact of several stressors such as temperature, 14 relative humidity, 15 partial pressure, 16,17 pH, 18 oxygen, 19,20 and particle sizes 8,21 on accelerating the long-term degradation process has been extensively reported in a series of experimental studies. Harzer et al 22 performed durability tests for a cathode with varying loadings under the exposure to different waveforms of accelerated stress tests (ASTs)square and triangularand analyzed its consequent effect on voltage cycling induced degradation.…”

“…The degradation mechanisms that occur in an operating environment along with their challenges, opportunities, and material evolution have been summarized in recent review articles. 10–13…”