Electroreduction of nitrite by hemin, myoglobin and hemoglobin in surfactant films

In this study we compare the electrocatalytic activity of hemin (Hm), myoglobin (Mb) and hemoglobin (Hb) embedded in surfactant films of didodecyldimethylammonium bromide (DDAB) cast on glassy carbon electrodes for the electroreduction of nitrite in phosphate buffer solution (pH=7.4). The electrocatalytic behavior was studied by cyclic voltammetry and rotating disk electrode (RDE) techniques. An electrocatalytic current was observed by both cyclic and RDE voltammetries at ca −1.1 V, close to the FeII/FeI redox couple, as previously reported. Our RDE investigations allowed us to observe a catalytic current at ca −0.1 V, close to the FeIII/FeII reversible process. This process was assigned to the first reduction process of the iron-nitrosyl adduct, which is rate determining, as evidenced by the Tafel slopes close to −0.12 V decade−1.