The apparent H 2 reaction order of γ = 0.65 for the exchange current density, as obtained from micropolarization analysis, is significantly different from one. At first glance, this might question the applicability of the mass-transport correction according to the KL equations (14) or (15). This led Rheinländer et al. to reconsider the KL-based mass-transport correction and devise a scheme that is applicable for non-unity reaction order. However, it must be noted that the reaction order of γ = 0.65 was extracted on an overpotential scale using the (shifting) RHE potentials under different H 2 partial pressures as potential reference.