ADSORPTION AND THE ELECTROCHEMICAL-BEHAVIOR OF ADSORBED HEMIN ON THE AMALGAMATED PLATINUM-ELECTRODE

Adsorption and the electrochemical behavior of adsorbed hemin is studi ed on an amalgamated platinum electrode. Hemin is shown to be strongly adsorbed on the electrode, as demonstrated by its reversible reductio n by the porphyrin ring in the supporting electrolyte. Under the condi tions that prevent the influence exerted by oxygen diffusion to the el ectrode, the redox reaction of the iron ion reduction in the center of hemin does not occur. However, in the presence of dissolved oxygen, a monolayer of adsorbed hemin displays the redox reaction in the potent ial region of possible Fe3+ reduction. Analyzing the data shows that, in this case, an oxygen complex with strongly-adsorbed hemin undergoes reduction. Depending on the hemin state in solution (monomer or dimer ), two forms of adsorbed hemin are observed. However, only one of thes e (dimeric form) is catalytically active in the oxygen reduction.