Effects of amphiphilic surfactants on electrolyte distribution in polymer electrolyte fuel-cell electrode
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Jin-Young Bae Department of Polymer Science and Engineering, Polymer Technology Institute, Sungkyunkwan University, Suwon, Kyunggi-Do 440-746, South Korea
Myung-Jin Lee,b) Hyuk Chang, and Do Young Seung Energy & Materials Research Laboratory, Samsung Advanced Institute of Technology, Suwon 440-600, South Korea (Received 22 April 2007; accepted 25 July 2007)
To enhance Pt utilization in the fuel-cell electrode by microscopically controlling the distribution of liquid electrolytes around Pt catalysts, the amphiphilic surfactant tergitol phosphate was synthesized and introduced into the fuel-cell electrode. The chemical structure of the surfactant was determined by 1H-nuclear magnetic resonance, and its adsorption property on Pt–C catalyst was ascertained by Fourier transform infrared analysis. The electrode into which the amphiphilic surfactants were incorporated showed improved performance, and especially the amphiphilic surfactant with polyethylene oxide, NPE10-OPO(OH)2, produced higher cell performance.
I. INTRODUCTION
Fuel cells have been attracting significant attention as future energy devices because of their high efficiency and environmentally friendliness. A high-temperature polymer electrolyte fuel cell (HT-PEFC) is especially much more promising due to its high Pt catalyst activity and tolerance to CO poisoning.1 The HT-PEFC uses phosphoric acid-doped polybenzimidazole as an electrolyte, and the phosphoric acid plays a role as a protontransferring medium. It is thus similar to a liquidelectrolyte-type fuel cell, such as a phosphoric acid fuel cell or a molten carbonate fuel cell. Accordingly, as in liquid-electrolyte-type fuel cells, it is more important to control the distribution and movement of a liquid electrolyte in an electrode.2–5 The conventional liquid-electrolyte-type fuel cells have used polytetrafluoroethylene as a binder or have regulated the pore size of an electrode. However, even in this case, there had been difficulties in managing the distribution and movement of the liquid electrolyte rigorously in the catalyst layer of the fuel-cell electrode, and so the catalysts in the electrode could not be used efficiently. Therefore, so far, a lot of research into improving Pt utilization has been performed by designing an elecAddress all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/JMR.2007.0417 J. Mater. Res., Vol. 22, No. 12, Dec 2007
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trode structure offering more three-phase boundaries for the electrochemical reaction. Here, by controlling the distribution and movement of the electrolyte in the neighborhood of the Pt catalysts, the enhancement of Pt utilization was tried. For this, the amphiphilic surfactants with hydrophilic and hydrophobic parts simultaneously were taken into consideration, and a novel amphiphilic surfactant was synthesized for the present HT-PEFC system. Several surfactants that have combinations of polyoxyethylene segments and alkyl chains having aci
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