Reversible and irreversible degradation in fuel cells during Open Circuit Voltage durability testing

Hin

et al. 2010

Durability issues have been attracting a great deal of attention in hydrogen/air proton exchange membrane (PEM) fuel cell research. In the present work, membrane electrode assembly (MEA) degradation under open circuit (OC) conditions was carried out for more than 250 h. By means of several on-line electrochemical measurements, the performance of the fuel cell was analysed at different times during the degradation process. The results indicate that structural changes in the PEM and catalyst layers (CLs) are the main reasons for the decline in performance during OC operation. The results also show that degradation due to platinum oxidation or catalyst contamination can be partially recovered by a subsequent potential cycling process, whereas the same cycling process cannot recover the membrane degradation.Crown

Section: Methodssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Effects of open-circuit operation on membrane and catalyst layer degradation in proton exchange membrane fuel cells

Zhang

Hin

et al. 2010

“…Since material degradation and lifetime change in a fuel cell are fully dependant on the operating conditions [3][4][5][6][7], the challenge of durability issues is mainly focused on the detailed understanding of failure modes and degradation mechanisms, as well as the systematic approaches to mitigate these problems [8]. Among the fuel cell components, the membrane electrode assembly (MEA) is considered to be the integral element, since it decides the maximum power density obtained from the electrochemical reaction.…”

Section: Introductionmentioning

confidence: 99%

“…Accelerated stress tests are more convenient to execute since they significantly reduce the experiment time while still providing valuable degradation information [16,17]. The accelerated stressors, such as open circuit voltage (OCV) operation [3], load/potential cycling [5], and freeze/thaw cycling [4,6] are the most common stressors used to study fuel cell degradation and failure modes. On the other hand, these test procedures can induce failure to the system that may not be related to actual operational conditions, which makes it hard to understand the exact causes and failure modes of degradation.…”

Section: Introductionmentioning

confidence: 99%

Diagnosis of MEA degradation under accelerated relative humidity cycling

Vengatesan

Fowler

et al. 2011

The objective of this work is to identify the failure mode diagnosis protocols for polymer electrolyte membrane (PEM) fuel cells with the use of accelerated testing conditions. The single cells used in this work were constructed using commercial Ion Power ® membrane electrode assemblies (MEAs) and the performance degradation was studied under accelerated dynamic reactant relative humidity (RH) conditions. The influence of RH on cell performance was investigated, and a strong dependence of degradation with respect to relative humidity was found. RH cycling was seen to not only cause the gradual decrease in performance at the beginning of cell operation, but it was also related to the rapid decline in performance observed after 330 h operation. This change in degradation rate is seen a change in the material degradation failure mechanism at this point in the operational history of the cell. The increase in cell resistance, membrane crossover, fluoride release rate and decrease in electrochemical surface area (ESA) were also observed with time, and these results were correlated to change in degradation rate. Infra-Red (IR) imaging of an aged MEA was utilized to show varying temperature profiles and outline the possibility of cracks, tears or pinholes in the membrane.

“…Open circuit (OC) operation has also been recognized as an effective stressor for accelerated testing and the accelerated effects of OC operation on the degradation of PEM fuel cell components, including the PEM and catalyst layers, have been investigated [11][12][13][14][15]. The increased gas crossover due to zero reactant consumption under OC conditions was believed to be the major reason for the high degradation rate of the membrane [16].…”

Section: Introductionmentioning

confidence: 99%

Degradation of a polymer exchange membrane fuel cell stack with Nafion® membranes of different thicknesses: Part I. In situ diagnosis

Zhang

Wang

et al. 2010

104

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. The durability of polymer exchange membrane (PEM) fuel cells, under a wide range of operational conditions, has been attracting intensive attention, as durability is one of the largest barriers for commercialization of this promising technology. In the present work, membrane electrode assembly (MEA) degradation of a four-cell stack with Nafion membranes of different thicknesses, including N117, N115, NR212, and NR211, was carried out for 1000 h under idle conditions. By means of several on-line electrochemical measurements, the performance of the individual cells was analyzed at different times during the degradation process. The results indicate that the cells with thinner membranes have a lower open circuit voltage (OCV) due to the higher fuel crossover. Before degradation, the thickness of the membranes correlates with performance of the cell. However, with the advancement of degradation, the performance of cells with thinner membranes degraded much faster than those with thicker membranes, especially after 800 h of operation. The fast performance degradation for thinner membranes is evident by a dramatic increase in hydrogen crossover indicating membrane thinning or pinhole formation. Crown