Electrocatalytic and adsorption properties of platinum microparticles electrodeposited into polyaniline films

The catalytic and adsorption properties of platinum microparticles incorporated into polyaniline films were investigated using methanol oxidation in acidic solutions as a test reaction. The potential dependences of the specific reaction rates — the stationary oxidation currents referred to the unit of the true platinum surface were measured for different amounts of incorporated platinum (25–750 μg cm−2). The methanol adsorption kinetics and the dependence of the surface coverage on methanol concentration were established. The results of adsorption measurements were compared with catalytic effects. It was found that the extent of the catalytic effects and their mechanism depend on the amounts of the microdeposits and their distribution in the polymer layer. For moderate and high platinum loadings (60–750 μg cm−2) the specific reaction rates are higher than those on platinized platinum and increase with increasing loadings up to the reaction rate on smooth platinum. At the same time the reaction mechanism for these electrodes remains the same. It seems that the catalytic effects on such electrodes are influenced by structural peculiarities of the deposits. For low platinum loadings (25–35 μg cm−2) a change in the ratio of the rate of different steps can be observed as methanol adsorption becomes markedly inhibited and limits the overall reaction rate.