FIELD DEPENDENCE AND ANOMALOUS TEMPERATURE DEPENDENCE OF TAFEL SLOPES FOR PROCESSES OCCURRING AT HIGH ELECTROSTATIC FIELDS

Publisher Website
Google Scholar
Abstract
A consideration of the probability per unit time for the transport of a charged species over a potential barrier in the presence of a high external electrostatic field shows that the net activation energy for such a process is in general a complex function of the field strength. Both the field dependence and the anomalous temperature dependence of the Tafel slope for the steady-state anodic oxidation of Ta, Nb, and Al are accounted for quantitatively by a simple model according to which the field independent component of the potential energy function for displacement of a mobile charged species is assumed to resemble a Morse function. Accordingly, the steady-state anodic oxidation data for these metals may be represented within experimental error by only three empirical constants, the pre-exponential factor, the activation energy, and the Morse function distance parameter. If, in place of a Morse function, a parabolic or cosine potential energy function is assumed, less satisfactory agreement with the data is obtained. Although there is some doubt concerning the uniqueness of the Morse function in explaining the data, there is no doubt that the present considerations are able to account entirely for the anomalous Tafel slope behavior.

This publication has 0 references indexed in Scilit: