Degradations in porous components of a proton exchange membrane fuel cell under freeze-thaw cycles: Morphology and microstructure effects |
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| Affiliation: | 1. Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada;2. 20/20 Laboratory for Fuel Cell and Green Energy RD&D, Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada;1. State Key Laboratory of Engines, Tianjin University, 135 Yaguan Road, Tianjin, 300350, China;2. Sunrise Power Co., Ltd., 907 Huangpu Rd., Hi-Tech Zone, Dalian, 116085, China;1. 20/20 Laboratory for Fuel Cell and Green Energy RD&D, Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada;2. Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada;1. 20/20 Laboratory for Fuel Cell and Green Energy RD&D, Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada;2. Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada |
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| Abstract: | In this study, porous components of a proton exchange membrane (PEM) fuel cell, i.e., single-layer gas diffusion layer (GDL, carbon paper), double-layer GDL (microporous layer (MPL) deposited carbon papers), and catalyzed electrodes, are subjected to 60 repetitive freeze-thaw cycles between −40 °C and 30 °C under water-submerged conditions; and their morphological and microstructural characteristics are investigated at each 15 cycles and compared with those of virgin materials. The results indicate that consecutive cycling of temperature causes different degradation patterns in different components. The single-layer GDL shows a unique degradation mechanism, in which macro-scale pores volumetrically expand, and relatively small-scale hollows and cracks form on the polymeric binder and carbon fiber interfaces, respectively. For the double-layer GDL, large-scale surface cracks form on the MPL surface after 15 cycles, and the morphology and microstructure degradation gains momentum with the formation of these cracks, and upon completion of 30 cycles, large-scale carbon/hydrophobic agent flakes start to detach from the surface. For the catalyzed electrodes, due to their inherently cracked surface, the catalyst layers (CLs) degrade first through expansion of the cracks in the in- and through-plane directions, and then through swelling and agglomeration of the ionomer; and combination of these two patterns triggers detachment of large CL flakes from the surface, negatively affecting the microstructure. |
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| Keywords: | Proton exchange membrane fuel cells Gas diffusion layer Microporous layer Catalyst layer Freeze-thaw cycles |
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