The kinetic parameters determined on a fixed potential scale provide new insight into the reaction mechanism of the alkaline HOR/HER. To this end, we compare the obtained kinetic parameters to the microkinetic rate laws of the various possible reaction mechanisms, which are presented in the supplementary material Eqs. (S27)-(S34). Here, we must distinguish different potential regions, for which we found differing results: HER parameters directly determined at larger (negative) overpotentials, HOR parameters directly determined at larger (positive) overpotentials, and HOR/HER model parameters fitted in the potential range around equilibrium. Moreover, in the latter range, two different sets of model parameters were obtained from Butler-Volmer fits with α a + α c = 1 and α a + α c = 2, respectively.