Electrocatalytic oxidation of methanol on Pt modified polyaniline in alkaline medium

A comparative study of the electrocatalytic oxidation of methanol is made in NaOH, Na2CO3 and NaHCO3 on bare Pt (Pt). polyaniline covered Pt (PANI) and Pt modified polyaniline film on Pt (Pt/PANI) using cyclic voltammetry, polarization, ac impedance spectroscopy and chronoamperometric techniques at 25 degrees C. The cyclic voltammetry and polarization studies show that the potentials at which methanol oxidation commences on different electrodes in each of the alkaline medium examined follow the trend Pt/PANI < Pt < PANI whereas the potentials for initiation of oxidation on each electrode in different alkaline media follow the order NaHCO3 > Na2CO3 > NaOH. The oxidation current is highest and charge transfer resistance lowest for Pt/PANI films compared to Pt in all the media studied. However, for the same Pt loading Pt/PANI films exhibit larger oxidation currents in NaOH followed by Na2CO3 and NaHCO3. The Tafel slope for methanol oxidation on Pt/PANI in NaOH, Na2CO3 and NaHCO3 has a value of about 115 mV decade(-1). The chronoamperometric response of the Pt/PANI film at the peak potential for methanol oxidation shows lesser sensitivity to poisoning by CO compared to bare Pt and platinised Pt (Pt/Pt). (C) 2008 Elsevier B. V. All rights reserved.