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Issue 12, 2012
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Thermal curing of PBI membranes for high temperature PEM fuel cells

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Abstract

Phosphoric acid doped polybenzimidazole (PBI) has emerged as one of the most promising electrolyte materials for proton exchange membrane (PEM) fuel cells operating under anhydrous conditions at temperatures of up to 200 °C. The limited long-term durability of the membrane electrode assemblies (MEAs) is currently hampering the commercial viability of the technology. In the present study, thermoset PBI membranes were prepared by curing the membranes under inert atmosphere at temperatures of up to 350 °C prior to the acid doping. The systematic membrane characterizations with respect to solubility, phosphoric acid doping, radical-oxidative resistance and mechanical strength indicated that the PBI membranes were irreversibly cured by the thermal treatment. After curing, the PBI membranes demonstrated features that are fundamental characteristics of a thermoset resin including complete insolubility, high resistance to swelling and improved mechanical toughness. Additionally, the thermal treatment was found to increase the degree of crystallinity of the membranes. The improved physicochemical characteristics of the membranes after curing were further illustrated by a dramatically improved long-term durability of the corresponding fuel cell MEAs. During continuous operation for 1800 h at 160 °C and 600 mA cm−2, the average cell voltage decay rate of the MEA based on the cured membrane was 43 μV h−1. This should be compared with an average cell voltage decay rate of 308 μV h−1 which was recorded for the MEA based on its non-cured counterpart.

Graphical abstract: Thermal curing of PBI membranes for high temperature PEM fuel cells

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Publication details

The article was received on 25 Sep 2011, accepted on 27 Dec 2011 and first published on 07 Feb 2012


Article type: Paper
DOI: 10.1039/C2JM14774B
Citation: J. Mater. Chem., 2012,22, 5444-5453
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    Thermal curing of PBI membranes for high temperature PEM fuel cells

    D. Aili, L. N. Cleemann, Q. Li, J. O. Jensen, E. Christensen and N. J. Bjerrum, J. Mater. Chem., 2012, 22, 5444
    DOI: 10.1039/C2JM14774B

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