This research discovers the burning reaction of the Pt/C catalyst on ink preparation and the effect of the untreated and burned Pt/C catalysts for the proton exchange membrane fuel cells (PEMFCs). The platinum nanoparticles on the carbon support aggregate to form bigger cluster sizes due to the burning reaction of the untreated Pt/C catalyst reacting with the Nafion solution or isopropyl alcohol. After several times of "purposely" burning reaction, the specific surface area of the fully burned Pt/C reduces from 150.9 to 46.6 m(2) g(-1) which is 3 times smaller than the untreated Pt/C catalyst. The crystallite size of platinum catalyst changes from 8.4 to 46.2 nm via the calculation of Debye-Scherrer equation from X-ray diffraction (XRD) and the electrochemical surface area (ECSA) obviously decreases from 85.6 to 14.8 m(2) g(-1). The variation of the ratio of Pt/C to Nafion influences the consequent electrochemical performances. Three catalyst coated membranes (CCMs) coated with untreated, fully burned, and partial burned Pt/C catalysts are analyzed and compared in this study. The CCM coated with the untreated Pt/C catalyst shows the best polarization curve which presents the peak power density, 897 mW cm(-2). Moreover, it presents the slowest degradation rate (0.1 mA min(-1)) at a constant voltage of 0.4V for 4000 min, even though the result of Nyquist plots is slightly worse than others The work confirms that the burning reaction of Pt/C catalyst influences the electrochemical performance and structural balance of the catalyst layer. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.