Durability of Membrane Electrode Assemblies (MEAs) in PEM Fuel Cells Operated on Pure Hydrogen and Oxygen

Abstract

Proton exchange membrane (PEM) fuel cells are energy sources that have the potential to replace alkaline fuel cells for space programs. Broad power ranges, high peak-to-nominal power capabilities, low maintenance costs, and the promise of increased life are the major advantages of PEM technology in comparison to alkaline technology. The probability of PEM fuel cells replacing alkaline fuel cells for space applications will increase if the promise of increased life is verified by achieving a minimum of 10,000 hours of operating life. Durability plays an important role in the process of evaluation and selection of MEAs for Teledyne's Phase I contract with the NASA Glenn Research Center entitled "Proton Exchange Membrane Fuel cell (PEMFC) Power Plant Technology Development for 2"d Generation Reusable Launch Vehicles (RLVs)". For this contract, MEAs that are typically used for HZ/air operation were selected as potential candidates for H2 / 0 2 PEM fuel cells because their catalysts have properties suitable for 0 2 operation. They were purchased from several well-established MEA manufacturers who are world leaders in the manufacturing of diverse products and have committed extensive resources in an attempt to develop and fully commercialize MEA technology. A total of twelve MEAs used in Hz/air operation were initially identified from these manufacturers. Based on the manufacturers' specifications, nine of these were selected for evaluation.Since 10,000 hours is almost equivalent to 14 months, it was not possible to perform continuous testing with each MEA selected during Phase I of the contract. Because of the lack of time, a screening test on each MEA was performed for 400 hours under accelerated test conditions. The major criterion for an MEA pass or fail of the screening test was the gas crossover rate. If the gas crossover rate was higher than the membrane intrinsic permeability after 400 hours of testing, it was considered that the MEA had failed the test. Three types of MEAs out of the nine total membranes failed the test.The evaluation results showed that fuel cell operating conditions (current, pressure, stoichiometric flow rates) were the parameters that influenced the durability of MEAs. In addition, the durability test results indicated that the type of membrane was also an important parameter for MEA durability. At accelerated test conditions, the MEAs with casted membranes failed during the 400 hour test. However, the MEAs prepared from the casted membrane with support as well as extruded membranes, both passed the 400h durability test at accelerated operating test conditions.As a result of the MEA accelerated durability tests, four MEAs were selected for further endurance testing. These tests are being carried out with four-cell stacks under nominal fuel cell operating conditions. This is a preprint or reprint of a paper intended for presentation at a conference. Because changes may be made before formal publication, this is made available with the understanding that it will not be cited or repr...

Study of Polymer Electrolyte Membrane Degradation under OCV Hold Using Bilayer MEAs

“…27 The lifetime of an MEA is frequently limited by mechanical breaches, such as pinholes or cracks, which result in rapid reactant crossover and subsequent cell/stack failure. 10,18,28 The material weakening and formation of mechanical defects can be revealed by a stress-strain test. Figure 4 shows the stress-strain behavior of the anode and cathode sides of the bilayer membrane and the behavior of the control samples superimposed in each graph.…”

A review of performance degradation and failure modes for hydrogen-fuelled polymer electrolyte fuel cells

“…The formation of thermal hot-spots has also been reported in the literature, as instigated through different mechanisms [173,174]. Hottinen et al [174] reported that a significant portion of the heat generated under the channel sections of the BPP has to flow in the in-plane direction.…”

“…The effect of uneven temperature distributions can be magnified when superimposed with inhomogeneous compression. Stanic et al [173] reported evidence of the formation of pinholes in regions where carbon fibres at the MEA-GDL interface created spots of high compression, accelerating membrane creep. High reaction rates in the vicinity of highly compressed membrane regions can raise the generation of heat energy, which also raises the local temperature.…”

Model-Based Analysis of the Limiting Mechanisms in the Gas-Phase Oxidation of HCl Employing an Oxygen Depolarized Cathode

“…These findings are in good agreement with theoretical and experimental insights in the field of classical PEM fuel cells stating that thinner membranes lead to a better water management by reducing the occurrence of membrane dehydration and thus the ohmic resistance. As both Stanic et al 47 as well as Springer et al 48 showed, a thinner membrane can significantly increase the limiting current by avoiding flooding of the cCL as well as dehydration of the membrane.…”