The proton exchange membrane fuel cells (PEMFC) have been developed mainly as a
power source for vehicles, power generation and consumer electronics since they combine high
energy conversion efficiency at relatively low temperatures without pollutants emission in the
environment. An electrode for a PEMFC is a layered structure composed by a catalyst layer
deposited on a porous carbon substrate. The substrate is usually covered by a diffusion layer that
enhances the gas and water flow. Platinum nanoparticles supported by carbon microparticles are
commonly employed as catalyst layer. In this work an extreme ultra-low loading of Pt catalyst (<
0.02 mg/cm2) has been deposited by magnetron sputtering on gas diffusion electrodes, with different
carbon supports (Vulcan and SuperP), in order to enhance the activity of PEM fuel cells. The
morphology (shape and grain size) and microstructure have been studied combining field emission
scanning electron microscopy (FEG-SEM), grazing incidence synchrotron x-ray diffraction
(GIXRD) and x-ray photoelectron spectroscopy (XPS). The results presented here concern the
evolution of the cluster size and shape after the ageing, induced by cyclic voltammetry for methanol
oxidation reaction.