Journal Article

PreJuSER-6269

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Membrane electrode assemblies for high-temperature polymer electrolyte fuel cells based on poly(2,5-benimidazole) membranes with phosphoric acid impregnation via the catalyst layers

Wannek, C.FZJ* ; Lehnert, W.FZJ* ; Mergel, J.FZJ*

2009
Elsevier New York, NY [u.a.]

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Please use a persistent id in citations: doi:10.1016/j.jpowsour.2009.03.051

Abstract: A novel strategy for introducing phosphoric acid as the electrolyte into high-temperature polymer electrolyte fuel cells by using acid impregnated catalyst layers instead of pre-doped membranes is presented in this paper. This experimental approach is used for the development of membrane electrode assemblies based on poly(2,5-benzimidazole) (ABPBI) as the membrane polymer. The acid uptake of free-standing ABPBI used for this work amounts to ABPBI x 3.1 H3PO4 which has a specific conductivity of similar to 80 mS cm(-1) at 140 degrees C. Rather thick catalyst layers (20% Pt/C, 1 mg Pt cm(-2), 40% PTFE as binder, d=100-150 mu m) are prepared on gas diffusion layers with a dense hydrophobic microlayer. After impregnation of the catalyst layers with phosphoric acid and assembling them with a mechanically robust undoped ABPBI membrane a fast redistribution of the electrolyte occurs during cell start-up. Power densities of about 250 mW cm(-2) are achieved at 160 degrees C and ambient pressure with hydrogen and air as reactants. Details of membrane properties, preparation and optimization of gas diffusion electrodes and fuel cell characterization are discussed. We consider our novel approach to be especially suitable for an easy and reproducible fabrication of MEAs with large active areas. (C) 2009 Elsevier B.V. All rights reserved.

Keyword(s): J ; Acid doping (auto) ; Catalyst layer (auto) ; High-temperature polymer electrolyte fuel cell (auto) ; Membrane electrode assembly (auto) ; poly(2,5-Benzimidazole) (auto) ; Phosphoric acid (auto)

Note: This work would not have been possible without Sina Chirayath's experience in and good intuition for the design and manufacture of catalyst layers for PEFCs. We would like to thank Irene Konradi for carrying out the water and acid uptake experiments, Egbert Wessel at Forschungszentrum Julich's IEF-2 for the SEM images, as well as Birgit Kohnen and Hans-Friedrich Oetjen for performing the fuel cell tests.This work was part of a joint project with FuMA-Tech GmbH funded by the German Federal Ministry of Economics and Technology under contract number 0326878A.

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Contributing Institute(s):

1. Brennstoffzellen (IEF-3)

Research Program(s):

1. Rationelle Energieumwandlung (P12)

Appears in the scientific report 2010

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