It is well established that the OHad has a decisive impact on the kinetics of ORR) on platinum surfaces. The appearance of OHNafion in the potential range of 0.84-0.94 V suggests that the presence of Nafion could have a significant impact on the oxygen reduction reaction (ORR) process on the Pt (111). The detrimental impact of Nafion on the ORR was typically attributed to site blocking by adsorbed sulfonate groups , however, this interpretation appears incomplete in light of creation of roughly two OHNafion per adsorbed sulfonate group. Before investigating the effect of Nafion adsorption on the ORR, it is necessary to confirm that sulfonate groups remain adsorbed during the reaction. CV features of sulfonate adsorption remain visible in an atmosphere of 80%Ar/20%O2, though the shape of the CV profile is significantly impacted by the currents attributable to the ORR (Figure ). This is the first experimental verification of the presence of adsorbed sulfonate in the potential window of interest for the ORR at the Nafion/Pt interface. Kinetic currents of the ORR on bare and modified Pt(111) surfaces were determined using the rotating disk electrode (RDE) method, with the impact of O2 diffusion corrected with the Koutecky-Levich equation .