Accelerated Membrane Durability Testing of Heavy Duty Fuel Cells

Abstract

Regular durability testing of heavy duty fuel cell systems for transit bus application requires several thousand hours of operation, which is costly and time consuming. Alternatively, accelerated durability tests are able to generate failure modes observed in field operation in a compressed time period, by applying enhanced levels of stress. The objective of the present work is to design and validate an accelerated membrane durability test (AMDT) for heavy duty fuel cells under bus related conditions. The proposed AMDT generates bus relevant membrane failure modes in a few hundred hours, which is more than an order of magnitude faster than for regular duty cycle testing. Elevated voltage, temperature, and oxidant levels are used to accelerate membrane chemical stress, while relative humidity (RH) cycling is used to induce mechanical stress. RH cycling is found to significantly reduce membrane life-time compared to constant RH conditions. The role of a platinum band in the membrane is investigated and membranes with Pt bands demonstrate a considerable life-time extension under AMDT conditions, with minimal membrane degradation. Overall, this research serves to establish a benchmark AMDT that can rapidly and reliably evaluate membrane stability under simulated heavy duty fuel cell conditions.

Progression in the Morphology of Fuel Cell Membranes upon Conjoint Chemical and Mechanical Degradation

“…12,17,26 Apart from the formation of chemically degraded locations in the membrane discussed in the previous section, other regions were found to undergo long range ordering of ion-rich domains until end-of-life. This could be perceived as mechanical stress induced morphological change 28 which is acting throughout the area of the membrane during the wet/dry cycles of the COCV-AST.…”

“…Such fractures could eventually propagate under mechanical stress into membrane-spanning cracks and pinholes observed macroscopically. 17,26 Imaging of macroscopic damage evolution would however require alternate techniques with higher field of coverage than TEM, which is subject to future work.…”

Local Impact of Pt Nanodeposits on Ionomer Decomposition in Polymer Electrolyte Membranes

“…[22], is confirmed by the observation that cells with PITM had a higher FER than the PITM-free cells. The controversy as to whether membrane degradation is increased or inhibited by PITM, as discussed in refs [19,[24][25][26][27], might be related to the influence of particle morphology and particle density. In ref.…”

“…The net rate of H 2 O 2 formation at PITM depends on the size, shape, and distribution of Pt nanoparticles in the membrane and local reaction conditions around particles, determined by temperature, electrical potential, reactant concentrations, pH, and RH [12][13][14][15][16][17][18][24][25][26][27][28][29][30][31].…”

Adjoint Method for the Optimization of the Catalyst Distribution in Proton Exchange Membrane Fuel Cells

“…In the area of automotive applications, PEMFCs have already been introduced commercially or for demonstration purposes by all the major car manufacturing companies; in addition, they are increasingly being used in busses, motorcycles, boats, submarines, and airplanes. 1,2 In the area of stationary and portable applications, PEMFCs are employed as emergency power systems, such as uninterrupted power supplies, and have the potential to be used for energy storage in electric grid systems. 3 Since the technical feasibility of PEMFCs has already been established, a significant amount of current research focuses on increasing the durability and decreasing the total manufacturing cost, which, at large manufacturing volumes, is mainly given by the cost of the catalyst layers (CLs), bipolar plates, and membrane.…”