The kinetic ORR current is inversely proportional to the charge attributed to the OHNafion on Nafion-covered Pt(111) with varying Nafion loadings (Figure , b, S13), suggesting that the presence of OHNafion is detrimental to ORR activity. Specifically, the ORR polarization curve on the Nafion-covered Pt(111) shifts cathodically by up to 25 mV at the current density of 1 mA/cm 2 compared with the bare Pt(111). The sulfonate adsorption and desorption peaks are much weaker on Aquivion-covered Pt(111) than those on Nafion-covered Pt(111) (Figure ). Nafion possesses an additional -OCF2CF(CF3)-fragement compared to Aquivion on the side chain, which makes its side chains more flexible and facilitates the specific adsorption of terminal sulfonate groups without causing significant strain to the backbone of the ionomer .