On the present understanding of the nature of inhibition of electrode reactions by adsorbed neutral organic molecules

Abstract

The discussion of the present state of understanding of the inhibition of electrode reactions by adsorbed organic compounds has been presented. It has been shown that the different models of the mechanism of inhibition may be reduced to the concept of competitive adsorption of activated complex, solvent and inhibitor molecules with different adsorption isotherms taken to describe adsorption of activated complex. On the basis of a statistical analysis of the literature data it has been shown that the inhibition may be well described by three different model equations originated from Flory-Huggins, Frumkin or Blomgren-Bockris adsorption isotherms for activated complex. Because of marked experimental errors both for the determination of the rate constant of the electrode process and the surface coverages of the electrode by the inhibitor, as well as a result of the impossibility or the proper correction of the rate constants for double layer effect it has been proved that the choice of the model of inhibition is not an ambiguous procedure if the measurements are carried out in the range of surface coverages 0<<1. The emphasis has been given to the importance of the study of the mechanism of inhibition in the region of full coverage of the electrode by inhibitor and the advantages of such investigations have been discussed.