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 map be deduced. An unusual combination of factors associated with a very low rate of dissolution of C-60 particles immobilised on glassy carbon and gold electrodes and a very rapid rate of dissolution OF reduced C-60 made it possible to investigate and model both solid-state and solution-phase aspects of the voltammetry of C-60 that occurs at an electrode-C-60-dichloromethane (electrolyte) interface. When an electrode containing adhered C-60 is placed in dichloromethane containing 0.10 mol l(-1) of n-Bu4NClO4, the reduction mechanism call be explained in terms of the scheme: [GRAPHICS] Alternatively, a square scheme involving C-60(-)(solid) may be operative in the initial stage of the reduction. The rate of dissolution of C-60 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 C-60 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 C-60 to C-60(-) in the solid state, restrictions based on solubility are eliminated and dissolution of adhered solid becomes very rapid. This stage of the dissolution process R:BS studied by cyclic voltammetry, single- and double-potential-step methods, chronocoulometry and microgravimetry, and again has been modelled. Q 2001 Elsevier Science B.V. All rights reserved.