Pt . It should be noted that Rheinländer et al. employed the symbol m for the reaction order of the exchange current density. Instead, we here use the symbol γ, because the reaction order of the exchange current density is equivalent to the reaction order defined under constant overpotential in Eq. ( ), for which the symbol γ is commonly used, while reserving the symbol m for reaction orders defined on a fixed potential scale. Mass-transport corrections. To extend the kinetic analysis beyond the micropolarization region, the data must first be corrected for mass transport effects. The hydrogen evolution reaction (cf. Eq. ( ) from the right to the left) is not affected by mass transport, because water is the reactant and available in excess. The hydrogen oxidation reaction (cf. Eq. ( )