We study the morphology of Nafion in the dilute IPA (isopropyl alcohol)/water mixture solutions containing 20-100 wt.% of IPA and in the Pt-C/Nafion gas diffusion electrodes (GDEs; where Pt-C is the carbon powder deposited on its surface with Pt particles), which are prepared by spraying on the carbon paper surfaces with a layer of Pt C, Nafion and IPA/water ink solution. The fuel cell performance of the GDEs strongly depends on the Nafion morphology in the ink solutions. A lower IPA content in the Pt-C/Nafion ink solutions results in the formation of larger and higher negatively charged Nafion aggregated particles, which leads to higher steric hindrance of the deposition of Nafion ionomer on the surface of Pt C particles and thus a thinner Nafion film in contact on the Pt C particle surfaces. The thinner Nafion film in contact with the Pt particles in the CL increases the chances of the Pt particles in contact with the H-2/O-2 gas, leading to a higher fuel cell performance. (C) 2012 Elsevier B.V. All rights reserved.