Four hundred hour fuel cell tests were performed on commercial, as-received and Ca 2+ contaminated catalyst coated membranes (CCMs) to evaluate the effects of long term exposure of foreign cations on fuel cell performance and degradation. Following testing, significant thinning of the cathode catalyst layer was observed across the entire active area in the contaminated cell, while only localized thinning was observed in the as-received baseline CCM. Analysis of the elemental maps and line intensity profiles of platinum (Pt) obtained from energy dispersive X-ray spectrum (EDX) shows minimal change in total platinum content across the thickness of the catalyst layer, and hence loss of carbon is suspected to be the cause of the thinning. A numerical model is employed to show the foreign cation redistribution during testing, which shows proton depletion in the cathode catalyst layer when the CCM is contaminated with foreign cations. We hypothesize that this lack of protons leads to accelerated carbon corrosion in the cathode to supply protons to oxygen reduction where foreign cations block transport of protons. A carbon corrosion scheme is presented which shows that under the operating potentials of the cell, carbon oxidation can occur, leading to the observed thinning. The polymer electrolyte fuel cell (PEFC), a promising clean energy source for automobile application, still needs to overcome durability issues originating from various sources.1 Cationic impurities originated from either ambient air (e.g. roadside contaminants) or from the corrosion of stack and balance of plant components can significantly decrease the performance and life time of PEFCs. [1][2][3][4] In this paper, we report on the influence of foreign cationic contamination on the thinning of the cathode catalyst layer during non-accelerated testing. Long duration (400hr) testing was conducted using commercial catalyst coated membranes which showed significant catalyst layer thinning in a calcium cation contaminated cell, this thinning of the cathode catalyst layer was not observed in a non-contaminated baseline. While foreign cations are known to cause several degradation mechanisms in PEFCs, no study has examined the influence of cationic contamination on carbon corrosion, which we believe causes the thinning of the catalyst layer.To understand the impact and mechanism of cation contamination in PEFC, several modeling 5-11 and experimental studies 12-33 have been conducted, including ex-situ contamination of the polymer membrane with various cations before the test as well as injecting cations into the air or fuel stream during the cell test. Okada and co-workers extensively investigated the effect of various metal cations (Li + , Na + , Ca 2+ , Fe 2+ , Ni 2+ , Cu 2+ , Rb 2+ , Cs + ) on the transport properties of perfluorosulfonic acid (PFSA) membranes, thermodynamics and oxygen reduction reaction (ORR) kinetics. 5,[13][14][15][16][17][18] They reported that, with the exception of Li + , all foreign cations have higher affinity toward the sulfo...

Chromium (Cr) poisoning is one of the major causes of cathode degradation in solid oxide fuel cells (SOFC). In this study, a computational model of Cr getter is discussed to optimize the design of getter for efficient capture of Cr and higher utilization. Monolithic substrate with 400 cpsi (cells per square inch) has been considered as the initial getter support structure with a coating thickness of 10 µm and 50% porosity. Design parameters include operating conditions of 1 kW SOFC system. Numerical results show that the getter design and configurations can be developed and optimized for systems life ranging from 40,000 to 50,000 hours. Initial experimental and modeling results are presented. Approaches for improving getter utilization and life are discussed.

Cationic contamination of polymer electrolyte fuel cells is known to cause performance degradation, particularly due to displacement of protons by foreign cations in the ionomer. Recent findings however, show that mass transport is a critical mechanism in the contamination process. X-ray computed tomography is used to examine the salt precipitation within the cathode diffusion media following in situ cation contamination experiments. Statistical analysis of the tomographic data is performed to examine the salt distribution inside a contaminated dual layer carbon paper substrate (GDL)-MPL. Results confirm the presence of salts on the surface, which is visually observable, but also show subsurface salts that are present up to the GDL-MPL interface. This new finding shows that cationic salts can precipitate in the macroporous carbon paper substrate, and the hydrophobic microporous MPL acts as a barrier to restrict cationic transport from reaching the fuel cell catalyst layer and membrane.

Cationic contamination causes reduction in PEM fuel cell performance and durability, two of the key factors limiting commercialization of the technology. Recent findings have shown that gas diffusion layers help prevent certain airborne particulate salts from reaching the membrane and catalyst layers. This paper uses micro x-ray computed tomography to examine the salt precipitation patterns in the GDL, and to understand how these affect the cell in terms of mass transport losses. The output of this analysis is a quantification of the changes in porosity after salt precipitation. Analysis shows that the crystallinity of the salt deposit is very dependent on the local amount of liquid water saturating the GDL and flow field. The salt build up can reduce local porosity of the GDL by 27%.