Charging Processes in Electroactive C60/Pd Films: Effect of Solvent and Supporting Electrolyte

Abstract

The electrochem. properties of solid films deposited on an electrode surface by simultaneous electrochem. redn. of C60 and palladium(II) acetate trimer in an acetonitrile/toluene mixt. have been studied using cyclic voltammetry. The electrochem. switching between the doped (conducting) and undoped (nonconducting) states involves both electron and ion transport within the film. The overall control of charge percolation through the C60/Pd electroactive material is governed by the transport of cations. The ion transport depends both on the nature of solvent and supporting electrolyte. The size of solvent mol. is the major factor detg. the degree of solvent swelling of the layer. In the case of small solvent mols., the C60/Pd film exhibits a reversible redox behavior. For larger mol. solvents, the voltammograms show a departure from reversibility. The redn. of the layer is accompanied by changes in its morphol. allowing for the solvent swelling of the film also in the case of large mol. solvents. The electrochem. response of the layer is not affected by the anions of the supporting electrolyte. However, a strong influence of both nature and concn. of supporting electrolyte cations on the redox properties of the layer is obsd., since these cations are incorporated into the C60/Pd layer. The redox ability in solns. contg. large cations is considerably reduced. The activation of the film at neg. potentials results in an increase of the doping level. The stability of the films is affected by the potential range over which they are examd. Scanning to highly neg. potentials results in the loss of redox activity due to removal of the film from the electrode surface.