Abstract: The electrochemical behaviour of poly-o-phenylenediamine (PPD)film coated electrode in pH 7. 0 phosphate buffer solution was studied by voltammetry and in-situ IRreflectance spectroscopy. The results showed that PPD exhibits redox activity at the potentials more negative than0.0V (SCE), and the redox process is accompanied by doping and undoping of H₂PO₄^- ions, showing that the polymer is positively charged. The reduction of benzoquinone at the PPD electrode occurs in the electroactive potential range of PPD. RDEexperiments indicated that benzoquinone is able to penetrate into the polymer matrix and exchange electron with the polymer. According to the model of PPD as a conducting polymer,the kinetics of benzoquinone reduction was analyzed and the influencing factors were discussed.

Key words: Conducting polymer electrode, Poly-o-phenylenediamine, Benzoquinone reduction, In-situ IR reflectance spectroscopy, RDE technique