While no mass-transport limitation is observed for the HER, limiting current densities of the order of 2-3 mA cm geo are reached for the HOR. Following previous recommendations, KL mass-transport corrections were restricted to RDE current densities up to half the limiting currents to avoid significantly amplified errors closer to the limiting current range. In addition, data points very close to the equilibrium potential had to be omitted in the general KL correction using Eq. ( ). This method relies on differences between rotation rates and thus is more susceptible to noise at very small currents than the simplified KL scheme using Eq. ( ). Kinetic currents of the HOR obtained from both KL methods are compared in Fig. for different hydrogen partial pressures, plotted on a fixed potential scale with the RHE potential under 100% H 2 saturation (p H2 ≈ 1 bar) as a fixed reference. For the simplified KL correction, only the results obtained from RDE data at 1600 rpm are shown.