The purpose of this study is to find an optimal mixture ratio of the platinum-loaded carbon catalyst and the electrolyte in a membrane electrode assembly (MEA) of a proton exchange membrane fuel cell for reducing the activation resistance, which influences the electrochemical surface area, activation polarization, and maximum power density of the MEA. First, mixture ratios of 10, 20, 40, and 60 wt% platinum-loaded carbon catalysts and electrolyte were examined. The results indicated that the fuel cell performance improved for mixing weight ratios of 1.0:2.0 in 10 wt% Pt/C, 1.0:1.8 in 20 wt% Pt/C, 1.0:1.1 in 40 wt% Pt/C, and 1.0:0.5 in 60 wt% Pt/C. Next, we evaluated the activation resistances of the MEA from the AC impedance characteristics using the optimal mixing weight ratio of the platinum-loaded carbon catalyst and the electrolyte. It was found that the activation resistances of the anode and cathode decrease with an increase in the weight ratio of platinum-loaded carbon in the catalyst layer. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.