Functionalization on the carbon material of PEM fuel cells providing them an ionic conductivity, has been thought as a promising way to improve the catalyst activity. Pt/Vulcan catalysts grafted with polystyrene sulfonate (PSSA) groups from 5 to 20 wt.% have been prepared. Owing to the ion-exchange properties of the PSSA grafted on carbon support, we developed less-Nafion electrodes, with only 0.25 or 0.50 mg cm− 2 Nafion loading. The effect of PSSA graft ratio and the Nafion amount was studied in a single cell at 30 °C by polarization curves and impedance measurements. It was found that 5 and 10 wt.% PSSA with 0.50 mg cm− 2 Nafion allow high efficiency, however lower than 10 wt.% grafted Pt/C with 0.25 mg cm− 2 Nafion only. The performance of the various electrodes could be correlated to the overall amount of sulfonate introduced: highest yields were obtained with an overall sulfonate concentration near 0.7–0.8 μmol cm− 2.