Influence of the composition on the structure and electrochemical characteristics of the PEFC cathode
2003 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 0019-4686, Vol. 48, no 28, 4175-4187 p.Article in journal (Refereed) Published
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 Nation are homogeneously mixed for any composition and no Nafion film was observed. The cathodes containing 36-43 wt.% Nation display a single or double Tafel slope behaviour ascribed to diffusion limitations in the agglomerates. At larger Nation 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.
Place, publisher, year, edition, pages
2003. Vol. 48, no 28, 4175-4187 p.
PEFC cathode, nafion content, electrochemical characterisation, material characterisation, agglomerate model, electrolyte fuel-cells, gas-diffusion electrodes, mass-transport limitations, catalyst layer, performance
IdentifiersURN: urn:nbn:se:kth:diva-22970DOI: 10.1016/s0013-4686(03)00603-0ISI: 000186645500009OAI: oai:DiVA.org:kth-22970DiVA: diva2:341668
QC 201005252010-08-102010-08-102010-10-14Bibliographically approved