Novel carbon aerogel supported Pt catalysts with different pore size distributions and Pt content have been synthesized and tested in a proton exchange membrane fuel cell (PEMFC) operation. Characterization of the aerogel supported Pt catalyst has been performed in respect to the total surface area of Pt using HRTEM and BET methods, and was compared to the electrochemical surface area of Pt in a cathode layer of the PEMFC by means of cyclic voltammetry. The effect of pore size distribution of the novel aerogel supported Pt catalyst on the performance of the PEMFCs, and kinetic parameters of the catalysts at different temperatures, is discussed in terms of the microstructure of the support and perfluorosulfonate-ionomer distribution. The PEMFC with a low Pt loading (0.1 mg/cm(2)) of a new porous aerogel catalyst has shown high power densities up to 0.8 mW/cm(2) in fuel cell operation conditions in air and at ambient pressure. (C) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.