Kinetic Isotope Effect for Metals with High Hydrogen Overpotentials

KINETIC ISOTOPE EFFECT FOR METALS WITH HIGH HYDROGEN OVERPOTENTIALS 

The rates of processes involving different hydrogen isotopes are generally different. This difference, called the kinetic isotope effect, can be easily characterized by the isotope separation factor S. For example, for a discharge reaction of proton and deuteron donors, this quantity is defined as the ratio of specific reaction rates  

The kinetic isotope effect is caused by two factors the effect of the mass of an isotope on the activation energy of the process (the change in zero-point energies), and its effect on the tunneling probability. Correspondingly, for any reaction, we can write S as the product of two factors, S and S.  

A cathodic evolution of hydrogen at a mercury and similar cathodes follows a slow discharge-electrochemical desorption mechanism. Naturally, the total rate of an isotope transition from solution to gas is determined not only by its discharge rate but also by the rate of its electrochemical desorption. Only the overall effect can be measured experimentally. Therefore, in order to calculate the observed isotope separation factor, we must write the balanced equation for the flux of proton and deuteron from liquid to gas[267]. 

It will be seen from the data discussed later that this value does 

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