Application and characterization of polypyrrole-modified electrodes with incorporated Pt particles

Abstract

Polypyrrole films of 0.3 μm thickness have been deposited on a carbon (vitreous carbon or pyrolytic graphite) or platinum substrate. Platinum particles have been deposited on this polymer layer in two ways. Firstly, by electrodeposition of the particles in and on the polymer layer by reduction of Pt4+ ions after the formation of polypyrrole, and secondly, by simultaneous deposition of polypyrrole and precipitation of Pt powder particles. Electrodes, prepared by the former method, proved to be electrocatalytically active for the oxidation of hydrogen in aqueous 0.5 M H2SO4, with high current densities at low Pt loading and low overpotential. The latter method produced electrodes with Pt particles, mostly inactive for the oxidation of H2. The electrodes with electrodeposited Pt particles were also active for the reduction of dioxygen, yielding (relatively) more H2O with increasing Pt loading and increasing rate of Pt deposition. A characterization of the electrodes with incorporated Pt particles was carried out, using AC-impedance techniques The ohmic resistance of the electrodes was determined as a function of the electrode potential and the Pt loading. The ohmic resistance of the electrodes increased, going from −0.2 V to −0.3 V vs SCE, due to the (partial) reduction of the polymer. Loading the polymer layer with Pt particles decreased the resistance at low potential (< −0.2 V vs SCE), depending on the rate of Pt deposition.