Hydrogen, electrode reactions isotope effect

An alternative application of cobalt Mb has been reported by Willner and coworkers (92). They immobilized the reconstituted cobalt Mb on the functionalized electrodes and generated cobalt(I)-Mb by the electrochemical reduction of cobalt(II)-Mb. The hydrogenation of acetylenedicarboxylic acid smoothly occurred on the functionalized electrode, and the electrocatalytic reaction in H20 and D20 reveals a clear isotope effect, kH/kD = 2.7, indicating that the hydride transfer from cobalt(III)-hydride in Mb is the key reactive process. 

In electrochemical proton transfer, such as may occur as a primary step in the hydrogen evolution reaction (h.e.r.) or as a secondary, followup step in organic electrode reactions or O2 reduction, the possibility exists that nonclassical transfer of the H particle may occur by quantum-mechanical tunneling. In homogeneous proton transfer reactions, the consequences of this possibility were investigated quantitatively by Bernal and Fowler and Bell, while Bawn and Ogden examined the H/D kinetic isotope effect that would arise, albeit on the basis of a primitive model, in electrochemical proton discharge and transfer in the h.e.r. 

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