Spectroelectrochemical and electrical characterization of poly(cobalt–tetraaminophthalocyanine)-modified electrodes: electrocatalytic oxidation of hydrazine

Polymeric complex films of cobalt–tetraaminophthalocyanine (Co–TAPc) and tetraaminophthalocyanine without the metallic center (H2–TAPc) were grown potentiodynamically on either glassy-carbon or conducting-glass electrodes. The electrolyte used in the electropolymerization was a 0.1 M tetrabutylammonium perchlorate–DMF solution containing the monomer. The modified electrodes were characterized by UV–Vis spectroscopy, voltammetry and electrochemical impedance spectroscopy. The role of the Co(II) center and the performance of these polymeric electrodes as electrocatalysts for hydrazine oxidation in aqueous solutions of pH 13 are discussed. The results indicated that Co(II) is the species acting as the electronic receptor of hydrazine, thus enhancing the electrocatalytic effect of the poly(Co–TAPc) electrode. This was also confirmed by the charge transfer resistance values from electrochemical impedance spectroscopy obtained during hydrazine oxidation, i.e. about 6×103 Ω on the poly (H2–TAPc) electrode and about 500 Ω on the poly(Co–TAPc) electrode.