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Hybrid Proton-Carrier Polymer Composites for High-Temperature FCPEM Applications

Published online by Cambridge University Press:  15 March 2011

F. J. Pern ,
J. A. Turner  and
A. M. Herring
F. J. Pern
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401
J. A. Turner
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401
A. M. Herring
Affiliation:
Department of Chemical Engineering, Colorado School of Mines, Golden, CO 80401
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Abstract

Hybrid proton-carrier polymer composites were fabricated in an effort to develop high-performance high-temperature proton exchange membranes (PEMs) for fuel cell applications in the 100°–200°C range. The solution-cast hybrid membranes comprise a polymer host and a SiO2-based proton-carrier composite that was synthesized via sol gel approach using a functional silane and tetraethoxysilane (TEOS) in acidic conditions. The primary H+-carrying component was either a heteropoly silicotungstic acid (STA) or a sulfonic acid (SFA) that was thermooxidatively converted from a mercapto (-SH) group. The embedding level of STA on the silane-modified SiO2 sol gel composites was strongly affected by the presence and the functional group of the silane. Ion exchange capacity (IEC) of the water-washed, SiO2-based STA and SFA proton-carrier composite powders is in the range of 1.8–3.5 mmol/g, two to three times higher than that for Nafion 117 (0.9 meq/mol). A glycidylmethacrylate-type copolymer, PEMAGMA, which is stable up to ∼225°C, was able to produce mechanically robust and flexible hybrid membranes. Upon curing, the PEMAGMA composite membranes showed a ∼75% gel under the present formulation and retained the "free" STA effectively with slight loss when extracted in an 85°C water. The W12-STA-containing PEMAGMA membranes followed the weight loss trends of water from STA and the SiO2-based sol gel composite, showing a 10 wt% loss at 150°C and a 15 wt% loss at 225°C. Fuel cell performance tests of the preliminary films gave a Voc in the 0.85–0.93 V range, but a low current density of <4 mA/cm2. The resistive characteristics were attributed to inhomogeneous distribution of the sol gel nanoparticles in the PEMAGMA matrix, a result of phase separation and particulate agglomeration during film forming.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 822: Symposium S – Nanostructured Materials in Alternative Energy Devices , 2004 , S8.6
Copyright
Copyright © Materials Research Society 2004

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