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• Yuan, T
• Zhang, H
• Zou, Z
• Khatun, S
• Akins, D
• Adam, Y
• Suarez, S
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• Zhang, H
• Zou, Z
• Khatun, S
• Akins, D
• Adam, Y
• Suarez, S
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• Zhang, H
• Zou, Z
• Khatun, S
• Akins, D
• Adam, Y
• Suarez, S

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Membranes 2012, 2(4), 841-854; doi:10.3390/membranes2040841

Article

A Study of the Effect of Heat-Treatment on the Morphology of Nafion Ionomer Dispersion for Use in the Passive Direct Methanol Fuel Cell (DMFC)

Ting Yuan ¹ , Haifeng Zhang ^1,* , Zhiqing Zou ¹ , Sufia Khatun ² , Daniel Akins ³ , Yara Adam ⁴  and Sophia Suarez ^4,*

¹ Shanghai Advanced Research Institute and Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 201210, China ² Physics Department, Hunter College of the City University of New York, New York, NY 10021, USA ³ CASI and Chemistry Department, The City College of the City University of New York, New York, NY 10031, USA ⁴ Physics Department, Brooklyn College of the City University of New York, Brooklyn, NY 11210, USA

* Authors to whom correspondence should be addressed.

Received: 14 November 2012 / Accepted: 26 November 2012 / Published: 6 December 2012

(This article belongs to the Special Issue Membrane Processes and Energy)

Download PDF Full-Text [1658 KB, uploaded 6 December 2012 12:05 CET]

Abstract: Aggregation in heat-treated Nafion ionomer dispersion and 117 membrane are investigated by ¹H and ¹⁹F Nuclear Magnetic Resonance (NMR) spectra, spin-lattice relaxation time, and self-diffusion coefficient measurements. Results demonstrate that heat-treatment affects the average Nafion particle size in aqueous dispersions. Measurements on heat-treated Nafion 117 membrane show changes in the ¹H isotropic chemical shift and no significant changes in ionic conductivity. Scanning electron microscopy (SEM) analysis of prepared cathode catalyst layer containing the heat-treated dispersions reveals that the surface of the electrode with the catalyst ink that has been pretreated at ca. 80 °C exhibits a compact and uniform morphology. The decrease of Nafion ionomer’s size results in better contact between catalyst particles and electrolyte, higher electrochemically active surface area, as well as significant improvement in the DMFC’s performance, as verified by electrochemical analysis and single cell evaluation.

Keywords: Nafion ionomer; aggregation; membrane electrode assembly; catalyst utilization; direct methanol fuel cell; NMR; viscosity

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