Cross-linked polybenzimidazole membranes for high temperature PEM fuel cells

Özdemir, Yağmur
Literature studies have shown that it is desirable to increase operation temperature of Proton Exchange Membrane Fuel Cells (PEMFCs) due to the reasons like reduced fuel impurity sensitivity, fast electrode kinetics, simple thermal and water management. However, during fuel cell operation at high temperatures, the PEM suffers from inevitable leaching out of the doped acid, which can have deteriorating effect on the membrane performance. Thus, there is always a need to minimize this problem by making ways so that the PBI based membrane can retain sufficient acid even at elevated temperatures. In this study, developing cross-linked PBI membranes for High Temperature PEMFC (HT-PEMFC) membranes with enhanced acid retention capability and better HT-PEMFC performance is the primary goal. Significant progress was made regarding the understanding of polybenzimidazole (PBI) chemistry. Extensive work has been conducted concerning preparation and characterization of covalently cross-linked PBI membranes. PBI membranes cross-linked by BADGE, DBpX, EGDE and TPA were prepared and their properties and performances were studied comperatively along with pristine PBI membrane. Membranes were characterized using acid doping, and acid leaching, proton conductivity, extraction in DMAc, SEM, TGA, and FTIR analyses in order to investigate the influences of cross-linking. The membranes prepared with TPA, BADGE and DBpX were tested in a single cell HT-PEMFC test unit. The membranes prepared with EGDE cross-linker was not studied further after the observation of nonpromising results. HT-PEMFC tests were conducted with dry air and H2 as reactants, at 1650C. The pristine PBI membrane based MEA reached to 0.085 maximum power density and 0.081 current density at 0.6 V. PBI-TPA-5 has shown the poorest performance among all the membranes with 0.051 maximum power density and 0.048 A.cm2 current density. PBI-DBpX-3 membrane gave 0.106 power density and 0.100 current density. The current density for PBI-BADGE-5 was found to be 0.121 and maximum power density was determined as 0.123 W.cm2. This is the highest performance obtained in this study. PBI-BADGE membranes were further investigated in order to determine the influence of cross linker content. Two additional sets of membranes with different cross linker content (2.5 and 7.5%) were prepared, characterized and tested. PBI-BADGE-7.5 showed maximum power density of 0.019, while PBI-BADGE-2.5 showed maximum power density of 0.027 After these results, PBI-BADGE-5 was found as the best performing membrane.


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High temperature polymer electrolyte membrane fuel cells (HT-PEMFC) are considered as the next generation of fuel cells since high temperature operation for PEM fuel cells has several advantages such as single phase operation, high carbon monoxide tolerance, low or zero carbon emission and removal of some equipment from the system. In order to obtain high performances, HT-PEMFC systems should be optimized in terms of dimensions, materials, operating conditions and other parameters. Modeling can help to pre-...
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Polybenzimidazole/SiO2 hybrid membranes for high temperature proton exchange membrane fuel cells
DEVRİM, YILSER; Devrim, Huseyin; Eroğlu, İnci (2016-06-22)
Polybenzimidazole/Silicon dioxide (PBI/SiO2) hybrid membranes were prepared and characterized as alternative materials for high temperature proton exchange membrane fuel cell (HT-PEMFC). The PBI/SiO2 membranes were cast from a PBI polymer synthesized in the laboratory and contained 5 wt. % SiO2 as inorganic filler. Scanning electron microscopy (SEM) analysis showed that the uniform and homogeneous distribution of SiO2 particles in the hybrid membrane. The existence SiO2 has improved the acid retention and p...
Development of self-humidifying nano-composite membrane for polymer electrolyte membrane fuel cell
Çaçan, Umut Baki; Özkan, Necati; Devrim, Yılser; Department of Polymer Science and Technology (2015)
Low humidity self-humidifying nano-composite membrane electrode assemblies (MEA) were developed for Polymer Electrolyte Membrane Fuel Cell (PEMFC) working at elevated temperatures. The nano-composite membranes were prepared by adding nano-sized silica particles (SiO2) or inorganic fillers with a size of approximately 20 nm to a polymeric material which is commercially named as Nafion (Perfluoro Sulfonic Acid/PFSA). The particle content of the nano-composite membranes were between 2.5 – 10 wt. %. In this man...
Citation Formats
Y. Özdemir, “Cross-linked polybenzimidazole membranes for high temperature PEM fuel cells,” M.S. - Master of Science, Middle East Technical University, 2018.