The electrocatalytic properties of adsorbed hemin and its nitrosyl adduct on glassy carbon surfaces toward hydroxylamine in aqueous neutral electrolytes

Cyclic voltammetry and dynamic and steady state polarization measurements have been used to examine the electrocatalytic activity of glassy carbon, GC, bearing a layer of adsorbed hemin, Hm, Hm|GC, toward hydroxylamine, NH2OH, in neutral aqueous solutions. The results obtained have provided ample evidence that Hm|GC promotes the reduction and oxidation of NH2OH, as well as its disproportionation. Also presented is a mechanistic model that accounts quantitatively for steady state polarization data for the reduction of NH2OH recorded with a Hm|GC rotating disk electrode, RDE. This model predicts that a very large fraction of the current is attributed to the reduction of a Hm species axially coordinated by a NH2OH molecule on one side and a nitrosyl group on the other at lower overpotentials and NH2OH on either side at higher overpotentials.