Inhibition of the electrooxidation of Cr(II) by adsorbed Cr(NCS) 3

Abstract

The electrooxidation of Cr(II) in the presence of 1–10 m M thiocyanate is inhibited over a wide potential range by adsorbed Cr(NCS) 3. Blocking of the electrode and a repulsive diffuse double layer effect appear to be the major inhibiting mechanisms. The inhibition is removed at anodic potentials probably by faradaic removal of Cr(NCS) 3 and at cathodic potentials by reduction of Cr(NCS) 3. Under the latter conditions an anodic “pseudo-prewave” is observed. The electroreduction of Cr(III)-thiocyanate complexes is discussed as it relates to the controlled potential electrooxidation of Cr(II) in the presence of thiocyanate and as it influences the electrooxidation of Cr(II).