Heyrovsky-Ilkovic plot

Draw a Heyrovsky-Ilkovic plot of In [(/j - /)//] against E. /d = 25.01 pA, because the current becomes limiting at higher E. The best straight line should have an intercept of 1/2 = -1.00 V and, from the gradient, the number of electrons (n) passed is 2. 

In Section 1.5 we used a graphical test for reversibility based on the Heyrovsky-Ilkovic equation. For a reversible reaction this gives a value of from an intercept on the plot. 

Much attention, particularly among the Russian workers, has been given to the applicability of the Heyrovsky-Ilkovic versus the Kolthoff-Lingane equation for electrode reactions involving metal deposition. In practice, one plots the electrode potential versus log[(/i — /)//] or log(/ — i) and examines the linearity of the plot and also the value of the slope (theoretically 2.3RTjnF). It is expected that the Heyrovsky-Ilkovic equation should be applicable when alloy formation with the electrode material takes place and the metal formed diffuses away from the surface so that its surface activity is a function of the current density. Alloying and diffusion in the electrode will be functions of the metal deposited, electrode material, temperature, and the rate of deposition (current density) therefore, comparison is difficult or meaningless if several of these variables are varied simultaneously. 

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