Electrocatalytic and adsorption properties of platinum microparticles electrodeposited into polyaniline films

The catalytic and adsorption properties of platinum microparticles incorpor ated into polyaniline films were investigated using methanol oxidation in a cidic solutions as a test reaction. The potential dependences of the specif ic reaction rates - the stationary oxidation currents referred to the unit of the true platinum surface were measured for different amounts of incorpo rated platinum (25-750 mug cm (- 2)). The methanol adsorption kinetics and the dependence of the surface coverage on methanol concentration were estab lished. The results of adsorption measurements were compared with catalytic effects. It was found that the extent of the catalytic effects and their m echanism depend on the amounts of the microdeposits and their distribution in the polymer layer. For moderate and high platinum loadings (60-750 mug c m (- 2)) the specific reaction rates are higher than those on platinized pl atinum and increase with increasing loadings up to the reaction rate on smo oth platinum. At the same time the reaction mechanism for these electrodes remains the same. It seems that the catalytic effects on such electrodes ar e influenced by structural peculiarities of the deposits. For low platinum loadings (25-35 mug cm (- 2)) a change in the ratio of the rate of differen t steps can be observed as methanol adsorption becomes markedly inhibited a nd limits the overall reaction rate. (C) 2001 Elsevier Science B.V. All rig hts reserved.