Modelling of solid-state, dissolution and solution-phase reactions at adhered solid–electrode–solvent (electrolyte) interfaces: electrochemistry of microcrystals of C60 adhered to an electrode in contact with dichloromethane (Bu4NClO4)

Frequently, dissolution processes accompany voltammetric investigations of solids adhered to electrode surfaces that are placed in contact with a solvent (electrolyte). However, rarely have such processes been modelled in order to determine what thermodynamic and kinetic information may be deduced. An unusual combination of factors associated with a very low rate of dissolution of C60 particles immobilised on glassy carbon and gold electrodes and a very rapid rate of dissolution of reduced C60− made it possible to investigate and model both solid-state and solution-phase aspects of the voltammetry of C60 that occurs at an electrode–C60–dichloromethane (electrolyte) interface. When an electrode containing adhered C60 is placed in dichloromethane containing 0.10 mol l−1 of n-Bu4NClO4, the reduction mechanism can be explained in terms of the scheme: atively, a square scheme involving C60−(solid) may be operative in the initial stage of the reduction. The rate of dissolution of C60 from a gold electrode surface at the open circuit potential and potentials prior to reduction was measured by the quartz crystal microbalance technique and shown to be dependent on the solubility of C60 in dichloromethane and the rate of diffusion of dissolved material into the bulk solution. Results were in good agreement with a simple theory developed to model the dissolution process. In contrast, after reduction of C60 to C60− in the solid state, restrictions based on solubility are eliminated and dissolution of adhered solid becomes very rapid. This stage of the dissolution process was studied by cyclic voltammetry, single- and double-potential-step methods, chronocoulometry and microgravimetry, and again has been modelled.