SEDL / STP / STP1056-EB / STP25284S

Correction of Experimental Data for the Ohmic Potential Drop Corresponding to a Secondary Current Distribution on a Disk Electrode

Esteban, JM
Graduate research assistant and associate professor, University of Florida, Gainesville, FL

Lowry, M
Graduate research assistant, University of Virginia, Charlottesville, VA

Orazem, ME
Graduate research assistant and associate professor, University of Florida, Gainesville, FL

Pages: 15    Published: Jan 1990

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Abstract

A numerical method is presented for adjusting experimental current-potential curves for the ohmic resistance corresponding to a secondary current distribution on a (rotating) disk electrode. The nonuniform current and potential distributions on the disk electrode cause the electrolyte resistance itself to be a function of measured current. The method described here is employed after the experiments are conducted and yields the Tafel slope as well as adjusted values for current density and surface overpotential that apply to the center of the disk. This facilitates the comparison of the experimental data to those obtained using mathematical models of the rotating disk electrode that, in the secondary current regime, apply strictly only to the center of the electrode. The Tafel slopes obtained agree to within 3 mV/decade with standard techniques for ohmic correction such as current interruption because, at the high current densities where the ohmic correction is most significant, the resistance correction approaches the primary resistance obtained by current interruption. The Tafel slope values for the two methods differ most for solutions of low conductivity. The major advantages of the ohmic correction method described here are that the experimental condition is never perturbed and that the method indicates the extent to which the current distribution is nonuniform.