ELECTROCATALYTIC OXIDATION OF H2O2 AT A COBALT PROTOPORPHYRIN MODIFIED ELECTRODE AND ITS APPLICATION IN ANALYSIS

The electrocatalytic behaviour of H2O2 oxidation at a cobalt protoporphyrin modified pyrolytic graphite electrode (CoPP/PG) in various pH buffer solutions has been investigated. In 0.1 M NaOH, a pair of quasi-reversible waves for the catalytic oxidation of H2O2 and the catalytic reduction of the product O2 at CoPP/PG appear. With decreasing solution pH value, the separation between both peaks on the cyclic voltammogram increases, and the electrode reaction becomes more irreversible. The formation, exchange and stability for the axial ligands on the CoPP molecules were explained with the Lewis acid-base theory. A possible scheme for H2O2 oxidation at the modified electrode is suggested. The i-E curve for H2O2 oxidation at a rotating CoPP/PG disc electrode displays a sharp peak instead of the normal S shape, which can be used to determine the H2O2 concentration in solution. A good linearity for the plot of peak current vs. H2O2 concentration was obtained. The detection limit can be as low as 5×10-7 M. © 1990.