Selective inhibition of electrode reactions by organic compounds

Abstract

Inhibition of different electrode reactions on Pt in acid solution by phenol was observed. The effect appears to be independent of charge or size of the reacting species. The oxidation of water molecules is unique in that it is almost unaffected by the addition of phenol under the same experimental conditions. Inhibition of I − oxidation was also found when substituted phenols were used. A correlation seems to exist between the ortho-para directing ability of a substituent in aromatic substitution reactions, its position with respect to the OH group in the substituted phenol, and the initial inhibition potential observed, which is a measure of the strength of the bond between the phenoxy radical and a metal atom at the surface. On the other hand, no correlation between the slope of E i vs. log c and the size of the inhibiting molecule ( i.e. the number of water molecules replaced from the surface) could be found 1,2 , although the two largest molecules tested, α- and β-naphthol, did give rise to the largest slopes, as expected.