The average and standard deviation of the Tafel slopes for oxygen reduction, obtained with the “activation control fit,” as a function of the cathodic window, w_c (see Figure 3). The black dotted line represents the Tafel slope of 0.24 V/dec, found with the “Tafel extrapolation” technique in domain A of the curve measured at 3,000 rpm in Figure 4. (a) 20 mV of the anodic branch is included in the fitting and (b) 40 mV of the anodic branch is included in the fitting.