Deterministic contact mechanics model applied to electrode interfaces in polymer electrolyte fuel cells and interfacial water accumulation

• Published in: Journal of power sources Vol. 241; pp. 379 - 387
• Main Authors: Zenyuk, I.V., Kumbur, E.C., Litster, S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2013; Elsevier
• Subjects: Applied sciences; Capillary pressure; Catalyst layer micro-porous layer interface; Compressing; Contact; Contact mechanics model; Contact resistance; Cracks; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Electrolytes; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Polymer electrolyte fuel cell; Size distribution; van Genuchten correlation; Voids; Water retention curve; Capillary pressure; van Genuchten correlation; Water retention curve; Catalyst layer micro-porous layer interface; Contact mechanics model; Polymer electrolyte fuel cell; Correlation; Polymer electrolytes; Polymer solid electrolyte; Mechanical contact; Porous material; Microporosity; Wettability; Deterministic model; Surface properties; Water holding capacity; Proton exchange membrane fuel cells; Solid electrolyte fuel cells; Catalyst; Interface; Electrode potential; Physicochemical properties
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2013.03.165

An elastic deterministic contact mechanics model is applied to the compressed micro-porous (MPL) and catalyst layer (CL) interfaces in polymer electrolyte fuel cells (PEFCs) to elucidate the interfacial morphology. The model employs measured two-dimensional surface profiles and computes local surface deformation and interfacial gap, average contact resistance, and percent contact area as a function of compression pressure. Here, we apply the model to one interface having a MPL with cracks and one with a crack-free MPL. The void size distributions and water retention curves for the two sets of CL|MPL interfaces under compression are also computed. The CL|MPL interfaces with cracks are observed to have higher roughness, resulting in twice the interfacial average gap compared to the non-cracked interface at a given level of compression. The results indicate that the interfacial contact resistance is roughly the same for cracked or non-cracked interfaces due to cracks occupying low percentage of overall area. However, the cracked CL|MPL interface yields higher liquid saturation levels at all capillary pressures, resulting in an order of magnitude higher water storage capacity compared to the smooth interface. The van Genuchten water retention curve correlation for log-normal void size distributions is found to fit non-cracked CL|MPL interfaces well. •Deterministic contact mechanics model applied to catalyst layer|MPL interface.•Direct imaging of sample surface topology for true morphology.•The cracked CL|MPL interface can store more water than the uncracked.•Cracks cover little contact area and cause minimal interfacial resistance.•van Genuchten water retention correlation shows a good agreement.