Ionicresistance and double layer capacitance of catalyst layer (CL) variationswith the thickness of the cathode CL were estimated byelectrochemical impedance spectroscopy (EIS) using the modified transmission-line model (TLM).0.1–0.4 mgPt cm−2 of commercial 20, 40, and 60 wt%Pt/C catalysts were used to control cathode CL thicknesses. Thecatalyst with a low Pt to C ratio was favorablefor maximum power density when the catalyst loaded was 0.2mgPt cm−2, and the catalyst with a high Pt toC ratio was favorable when catalyst loading was 0.3 mgPtcm−2. The electrochemical surface areas of 20, 40, and 60wt% Pt/C were different, whereas the Pt utilization of thesecatalysts was similar. Modified TLM under the non-faradaic condition wasused for an easy estimate of the ionic resistance anddouble layer capacitance of the CL. Moreover cell inductance, electrolyteresistance, and the charge transfer resistance of crossovered H2 wereused for a precise estimate. The ionic resistances and doublelayer capacitances of the CL were linearly proportional to CLthickness regardless of the Pt to C ratio.
©2012 The Electrochemical Society
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