3D Failure Analysis of Pure Mechanical and Pure Chemical Degradation in Fuel Cell Membranes

Abstract

Lifetime-limiting failure of fuel cell membranes is generally attributed to their chemical and/or mechanical degradation. Although both of these degradation modes occur concurrently during operational duty cycles, their uncoupled investigations can provide useful insights into their individual characteristics and consequential impacts on the overall membrane failure. X-ray computed tomography is emerging as an advantageous tool for fuel cell failure analysis due to its non-destructive and non-invasive 3D imaging capabilities at ambient conditions. In the present work, post-mortem failure analysis of pure mechanical and pure chemical membrane degradation modes is performed three-dimensionally using this technique. A uniquely comprehensive analysis afforded by this technique reveals that membrane failure is almost exclusively characterized by crack formations during mechanical degradation and by severe thinning accompanied by electrode shorting and pinhole formation during chemical degradation, respectively. Catalyst layer cracks, particularly on the cathode side, are found to interact strongly with mechanically induced membrane cracks. The conjoint effect of chemical and mechanical stressors is established as a necessary requirement for: (i) exclusive membrane crack development independent of catalyst layer cracks; and (ii) crack branching during membrane crack propagation. Overall, the membrane failure analysis improves its reliability and quantitative character with the adoption of 3D imaging. The transportation sector is a significant contributor to global greenhouse gas emissions and with ever-growing concerns around the global warming effect, research and development of novel clean energy based automotive solutions is being pursued worldwide. Hydrogen fuel cells have thus far emerged as a promising alternative to fossil fuel based internal combustion engines due to their clean, noisefree, and efficient operation.1 Polymer electrolyte membrane (PEM) fuel cells 2 are widely used in fuel cell electric vehicles (FCEVs) and supply electrical energy from the electrochemical conversion of hydrogen and oxygen (usually supplied as air) into water. In automotive applications, the fluctuating operating conditions due to vehicle dynamics, variations in loads and environmental conditions, startups and shutdowns, fuel starvation, contamination, and freeze-thaw cycles pose significant durability challenges for the PEM fuel cells. 3Understanding the specific durability problems and developing suitable solutions remains a key research focus in automotive PEM fuel cell technology research and is critical to the long-term and large-scale commercial adoption of this technology. Given the complex interplay of multiple physical phenomena that are simultaneously active in an operating PEM fuel cell, various deleterious factors affecting PEM fuel cell components can collectively lead to a gradual performance loss and eventual failure.In PEM fuel cells, the electrodes are separated by a polymeric membrane which allows selective tran...

Biaxial fatigue crack propagation behavior of ultrahigh molecular weight polyethylene reinforced by carbon nanofibers and hydroxyapatite

“…Symmetrical branching was predicted, and it was in good agreement with the experimental observations found in the literature. But at the same time, they also pointed out that the size of the specimen and the type of material may relevantly influence the crack path, which was confirmed by Singh, Orfino, Dutta, and Kjeang () in a research on the failure analysis of fuel cell membranes handled with chemical or mechanical degradations. It was found that bifurcation cracks occurred only when mechanical degradation and chemical degradation acted simultaneously, which was explained that the material embrittlement caused by chemical degradation makes cracks easier to propagate.…”

Influence of the Catalyst Layer Structure Formed by Inkjet Coating Printer on PEFC Performance

“…In addition, from the perspective of cell durability, several researchers reported that cracks in the CL reduces cell durability [ 30 , 31 , 32 ]. Consequently, it is desirable to study the ink exhaling method that suppresses the occurrence of cracks.…”

Research Progress of Proton Exchange Membrane Failure and Mitigation Strategies

“…Aindow et al [ 17 ] simulated the stress state of PEM during humidity cycle by ex-situ mechanical fatigue experiment, drew the stress cycle failure curve to predict the mechanical durability of the membrane under humidity cycle, and predicted the residual life of PEM by comparing the fatigue test data of the initial and the degraded samples. Singh et al [ 18 , 19 ] induced the pure mechanical membrane degradation by 0%–90% RH cycling accelerated test, that indicates a high crossover leakage near the gas inlet (as shown in Figure 2 ), which is indicator of preferentially severe mechanical degradation. At the same time, it was found that the cracks in the catalyst layer (especially the cracks on the cathode side) have a high mechanical stress concentration effect on the PEM contacting with it, which promotes the crack propagation of PEM.…”