OXIDATION OF FORMIC-ACID AT PLATINUM MICROPARTICLES DISPERSED IN A POLYANILINE MATRIX - INFLUENCE OF LONG-RANGE ORDER AND METAL-POLYMER INTERACTION

The effects of long-range order and deposition of platinum microparticles on the activity of polyaniline films synthesized at various temperatures have been investigated. The degree of long-range order in the polymer has a pronounced influence on the electrochemical behaviour of polyaniline which consequently affects the deposition of metal particles into the polymer matrix and finally the catalytic activity. The steady-state rates of oxidation of formic arid at polyaniline-coated electrodes, (PAn), synthesized at 0, 22 and 40°C are an order of magnitude higher than the rate at a platinized platinum electrode at 0.1 V vs. SCE. Modified polyaniline-coated electrodes (MPAn) (for the polymer synthesized at 22°C), show a hundred-fold increase in activity as compared to bulk platinum. MPAn synthesized at 0°C shows little enhancement in activity while greater enhancement (but lower than 22°C) was observed for 40°C polymer. The CVs obtained with platinized polymer electrodes were subject to numerical deconvolution in order to obtain the "true" electrocatalytic currents at the platinum microparticles. The deconvoluted CVs provide striking evidence of the similarity of the electrocatalytic currents due to the microparticles in all three polymers and the catalytic effects arising from polymer-metal interaction. A comparison of the catalytic activity with the resistance profiles shows that the oxidation currents are limited by the resistance of the polymer films. © 1990.