. This procedure ensures that there are enough data points to reliably determine the fit parameters. The RHE potential for p H2 = 1 bar was used as a common potential reference and the data was fitted in the potential range from -0.02 to +0.04 V vs. RHE(1 bar). Fitted curves are shown in Fig. , where the kinetic current data obtained from the general KL correction (Eq. ( )) was used, and the fitted parameter values are summarized in Table . For both α a + α c = 1 and α a + α c = 2, we obtained high-quality fits of the experimental kinetic current curves with the generalized Butler-Volmer model. This is somewhat contradictory to the conclusion by Rheinländer et al., who discarded the fits with α a + α c = 2. The discrepancy to our finding might be attributed to the different fitting approach followed in our study, namely fitting of the entire data set at once under multiple H 2 concentrations on a fixed potential scale. Interestingly, visual inspection of the fitted curves in Fig. ,b reveals a slightly better agreement of the fits with α a + α c = 1 in the HOR region, while fits with α a + α c = 2 have a slightly better match in the HER Table : Results of the generalized Butler-Volmer fits performed on a fixed potential scale. The sum of the transfer coefficients, α a + α c , was kept fixed at either 1 or 2. Accordingly, α c is given by α c = 1 -α a or α c = 2 -α a , respectively.