Influence of Uncompensated Solution Resistance Upon the Evaluation of Rate Constants for Rapid Electrochemical Reactions

摘要

We have recently outlined an experimental method whereby the relibility of observed standard rate constants for outer-sphere electrochemical reactions, evaluated using a given technique and a set of experimental conditions can be tested in a direct manner. This entails monitoring the response of the 'apparent observed' values of standard rate constants, apparent observed rate constants, to systemic alterations of the strongly double-layer structure caused by the addition of small concentrations of specifically adsorbing anions. This procedure enables standard rate constants for the test reaction to readily be 'tuned' over toa wide range. These apparent rate variations, are compared with those observed under the same conditions for a structurally similar, yet irreversible, 'calibration' reaction having rate constants in the range ca. .0001 to .01 cm/sec, where they can be evaluated reliability using straightforward d.c. methods. This comparison enables the extent of departure of apparent observed rate constants from the corresponding 'true' rate constants, for values that approach the suspected measurement limit to be obtained, provided that the data set also includes sufficiently small values of apparent observed rate constants.