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The Effect of Microporous Layer in Phosphoric Acid Doped Polybenzimidazole Polymer Electrolyte Membrane Fuel Cell

Muhammet Çelik, Gülsah Özisik, Gamze Genç and Hüseyin Yapici

A polybenzimidazole (PBI) based polymer electrolyte fuel cells, which called high temperature polymer
electrolyte fuel cells (HT-PEMS), operate at higher temperatures (120-200°C) than conventional PEM fuel cells. Although it is known that HT-PEMS have some of the significant advantages as non-humidification requirements for membrane and the lack of liquid water at high temperature in the fuel cell, the generated water as a result of oxygen reduction reaction causes in the degradation of these systems. The generated water absorbed into membrane side interacts with the hydrophilic PBI matrix and it can cause swelling of membrane, so water transport mechanism in a Membrane Electrode Assembly (MEA) needs to be well understood and water balance must be calculated in MEA. Therefore, the water diffusion transport across the electrolyte should be determined. In this study, it is investigated firstly the water content in a MEA in the case of with/without Microporous Layer (MPL). Secondly, in the case of with MPL the effect of microporous layer’s thickness on the water management in fuel cell is investigated. For this aim, two-dimensional fuel cell with interdigitated flow-field is modeled using Comsol Multiphysics 4.2a software. The operating temperature and doping level is selected as 180°C and 6.75 RPU H3PO4/PBI, respectively. The results of
this work brought out that MPL significantly effects to water content in MEA and reduces H2O concentration in MEA. Thus it can be prevented to flooding in MEA and so durability of the cell is increased.