Influence of the composition on the structure and electrochemical characteristics of the PEFC cathode

The influence the composition of the cathode has on its structure and electrochemical performance was investigated for a Nafion content spanning from 10 to 70 wt.%. The cathodes were formed on a Nafion membrane by the spray method and using 20 wt.% Pt on Vulcan (E-TEK). Materials characterisation (S...

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Bibliographic Details
Published in:Electrochimica acta 2003-12, Vol.48 (28), p.4175-4187
Main Authors: Gode, Peter, Jaouen, Frédéric, Lindbergh, Göran, Lundblad, Anders, Sundholm, Göran
Format: Article
Language:English
Subjects:
Agglomerate model
Applied sciences
catalyst layer
Chemistry
Electrochemical characterisation
electrolyte fuel-cells
Energy
Energy. Thermal use of fuels
Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc
Exact sciences and technology
Fuel cells
gas-diffusion electrodes
Kemi
mass-transport limitations
Material characterisation
Nafion content
NATURAL SCIENCES
NATURVETENSKAP
PEFC cathode
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Summary:The influence the composition of the cathode has on its structure and electrochemical performance was investigated for a Nafion content spanning from 10 to 70 wt.%. The cathodes were formed on a Nafion membrane by the spray method and using 20 wt.% Pt on Vulcan (E-TEK). Materials characterisation (SEM, STEM, gas and mercury porosimetry, electron conductivity) and electrochemical characterisation (steady-state polarisation curve, impedance spectroscopy in O 2 and current-pulse measurements in N 2) were performed. The impedance spectra were analysed using our dynamic agglomerate model. The results indicate that the agglomerate model is valid until a Nafion content of about 45 wt.%. Pt/C and Nafion are homogeneously mixed for any composition and no Nafion film was observed. The cathodes containing 36–43 wt.% Nafion display a single or double Tafel slope behaviour ascribed to diffusion limitations in the agglomerates. At larger Nafion content, the agglomerate model can describe the curves only by assuming a diffusion coefficient 3–4 decades smaller than that of gases. At such compositions, the porosity was only 10%. These results were interpreted as a blocking of the pores and a non-percolating pore system for too large Nafion contents.
ISSN:0013-4686
1873-3859
1873-3859
DOI:10.1016/S0013-4686(03)00603-0