DIRECT DETERMINATION OF THE TRANSFER COEFFICIENT FROM CYCLIC VOLTAMMETRY - ISOPOINTS AS DIAGNOSTICS

摘要

Isopoints are observed when cyclic voltammograms recorded at several scan rates are all plotted on the same potential axis, The isopoint is the point where all curves intersect. Here, isopoints are used as a diagnostic under reversible and quasireversible electron transfer conditions, A method is presented for determining the transfer coefficient, alpha, using only the isopoint potential, switching potential, and peak potentials, all readily identifiable points on the voltammograms, It is not necessary to know the diffusion coefficients, standard rate constant, standard potential, electrode area, or solution concentration to apply this method, The isopoint method is applicable for differences in peak potentials of 0.073-0.145 V. The method is verified experimentally by comparing the values of a determined by the isopoint and convolution methods, A linearization of the dimensionless kinetic parameter, psi, developed by Nicholson, with the difference in peak potentials is presented, It is also shown that the average of the peak potentials yields the half-wave potential within 1 mV for differences in the peak potential of less than approximately 0.145 V. Ah models were developed by computer simulation (Digisim).