Simulation Analysis of Errors in the Measurement of Standard Electrochemical Rate Constants from Phase-Selective Impedance Data

摘要

A digital simulation analysis is presented of the coupled effects of solution resistance and lock in amplifier damping upon the evaluation of standard rate constants for rapid electrode reactions using phase-selective AC impedance measurements with positive-feedback iR compensation. These two effects combine so to yield apparent (i.e. measured) rate constants, evaluated using the conventional frequency-dependent analysis that are generally smaller than the actual values. The extent to which these systematic errors depend on experimental conditions is explored for various values the uncompensated and specific solution resistances, the amplifier filter time constant, the double layer capacitance and other relevant parameters. A simple scheme employing these simulations is outlined by which the actual values can be extracted from apparent measurements. Some experimental verification of these effects is also presented.