KINETIC-STUDY OF ELECTROCATALYTIC REDUCTION OF HYDROGEN-PEROXIDE AT IRON(III) PORPHYRIN MODIFIED GLASSY-CARBON ELECTRODE IN ALKALINE-MEDIUMUSING THE ROTATION-SCAN METHOD

Reduction of hydrogen peroxide at a glassy carbon (GC) electrode modif ied with sigma-bonded pyrrole iron(III) octaethylporphyrin complex, (O EP)Fe(Pyr), was studied by cyclic voltammetry and a rotating disk elec trode. In 0.1N NaOH solution, it is shown that such an (OEP)Fe(Pyr)/GC electrode has a significant catalytic activity towards hydrogen perox ide reduction (E(D) = -0.80 V, k = 0.066 cm s(-1)); however, the elect rode stability is low. The deactivation is observed when the reaction charge (Q) is passing through the (OEP)Fe(Pyr)/GC disk electrode. A li near rotation scan method is applied to study the kinetic process by d etermining the disk electrochemical response (i(D)) to rotation rate ( omega) at a definite disk potential (E(D)). Considering that the numbe r of adsorbed electroreduced catalyst molecules (Red) varies according to the disk potential, a factor theta(= Gamma(Red)/(Gamma(Red) + Gamm a(Ox))) is introduced to describe the electrode surface area fraction for electroreduced species. The obtained Koutecky-Levich equation is a pplicable whatever the potential is.