The electronic effects from the coverage can then be described by relative changes on the binding energy, thus allowing us to use the previously introduced quantity Λ in a form of a further defined (positive) function Λ(𝜃). This formulation allows approximating the classical Langmuir type isotherm but can also produce isotherms whose coverage increases beyond unity, see Fig. We have yet to discuss effects of molecular hydrogen which we, in accordance with the accepted theory of the H-upd, have not incorporated in its kinetic description. Similarly, the rate constant is per definition expected to be independent of reactant activities (hence its name) which instead are being accounted for in its determination. Therefore, the rate constant should also be independent of the pH and only change when the reaction itself changes, e.g. from the acidic to the alkaline H-upd oxidation/formation (except for secondary energetic effects on the activation barrier). We have performed an exhaustive survey of both properties and find substantial discrepancies from these expectations. First, 𝐸 𝑝,∞ should thermodynamically be constant on a pH-adjusted potential scale. We observe a systematic deviation from such relationship for the acidic peak positions (Fig. ). In our publication on pH buffers , we demonstrate that this shift is caused by the onset of mass transport limitations and would otherwise follow the Nernstian relationship. In the alkaline regime, beyond the anion-switch pH values, 𝐸 𝑝,∞ remains relatively constant for the same combination and concentration of cations and anions, with non-trivial variations between different electrolyte compositions. Secondly, the rate constant, both in the acidic and alkaline regime exhibits an unexpected ideal Nernstian shift (Fig. ). This effectively compensates for the role of the activities of hydronium and hydroxyl ions given in its determination, meaning that the H-upd kinetics act as if hydronium and hydroxyl ions play no role in the reaction. This is contradictive to the confirmation of the Nernstian shift of 𝐸 𝑝,∞ and the behavior of the peak separation in hydronium and hydroxyl ion deficient conditions. In Fig. we have also plotted in the inset the rate constant for such case where the reaction rate of the H-upd does not dependent on the activity of hydronium and hydroxyl anions and find a value of around 20 nmol/cm 2 s in acidic and 5 nmol/cm 2 s in alkaline conditions. We have yet not found a mechanistic description that can account for such a behavior and, in the absence of experimental and theoretical errors, the currently accepted classical theory of the H-upd must be incomplete. Instead, we can perform a simple functional analysis: We know that the ratio of the proton acceptor and donor pair must equal the pH to obtain the expected, and in alkaline media confirmed, Nernstian pH shift ∆𝐸 𝑝𝐻 (Eq. 50a). ( ) Naturally we would like the classical Volmer step of the H-upd to be valid description of its kinetics but must make sure that the pH has no role in the dimensionless scan rate (Eq. 45) so that the effective activity (Eq. 44a) around the H-upd peak is independent of pH (Eq. 50b).