We then compared this model with respect to our experimental observations (see Fig. ), both in terms of general properties which are not sensitive to the model parameters and specific properties which are sensitive to the model parameters. The general properties are that (1) the HER increases exponentially with potential due to the unbounded hydrogen coverage with a Tafel slope of around 175 mV/decade, and (2) the reaction order of the micropolarization exchange current density for molecular hydrogen and hydroxide ions is 0.5 and 0 respectively. It is worth noting that the Tafel slope is not very sensitive to interaction function Λ(𝜃) (Eq. 54e, obtained from the numerical model). These results are in excellent agreement with experimental observations, see e.g.