PEMFC is a conversion device that uses the chemical energy of the O2/H2 pair to produce electricity, heat, with water as a by-product. The main component of the individual cells composing the PEMFC is the Membrane Electrode Assembly which is composed of a proton conducting polymer electrolyte membrane sandwiched between two electrodes. The electrode is a key and critical component, in terms of cost, performance and durability, as it is the place of the electrochemical reactions. The electrode is made of platinum nanoparticles (2-5 nm) supported on electrically conductive mesoporous carbon particles (~30-50 nm) which are bound in a proton conducting polymer, the ionomer. The proposed experiment aims at investigating the effect of solvent, catalyst and ionomer types on the ionomer nanostructure. This study will help for a better understanding of the influence of the fabrication process on the structure and dispersion of the ionomer in the electrode.