Potential Relation for Electron Transfer at the Electrode

Current-Potential Relation for Electron Transfer at the Electrode 

Two processes can occur at the electrode surface one is the process in which Ox is reduced to Red by accepting electron(s) from the electrode and the other is the process in which Red is oxidized to Ox by donating electron(s) to the electrode. If we express the rate of the reduction, i.e. the amount of Ox reduced per unit surface area and per unit time, by vf (mol cnT2 s 1) and that of the oxidation by Vb (mol cm 2 s 1), they are given by Eqs (5.2) and (5.3)  

When Vf=Vb, the electrode reaction is in equilibrium and no change occurs overall. The potential at which the reaction is in equilibrium is the equilibrium potential. If we express it by Eeq (V), we get the following Nernst equation from Eqs (5.2) and (5.3)  

1) The transfer coefficient, a, is a measure of the symmetry of the energy barrier in the reaction coordinate and is often between 0.3 and 0.7. Here we simply consider that, when the electrode potential changes by AE, the fraction aAE 

A is the electrode surface area (cm2) and, in this book, a positive current value is assigned to the reduction current and a negative current value to the oxidation current. 

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