Modelling of solid-state, dissolution and solution-phase reactions at adhered solid-electrode-solvent (electrolyte) interfaces: electrochemistry of microcrystals of C-60 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 solv ent (electrolyte). However, rarely have such processes been modelled in ord er to determine what thermodynamic and kinetic information map be deduced. An unusual combination of factors associated with a very low rate of dissol ution of C-60 particles immobilised on glassy carbon and gold electrodes an d a very rapid rate of dissolution OF reduced C-60 made it possible to inve stigate and model both solid-state and solution-phase aspects of the voltam metry of C-60 that occurs at an electrode-C-60-dichloromethane (electrolyte ) interface. When an electrode containing adhered C-60 is placed in dichlor omethane containing 0.10 mol l(-1) of n-Bu4NClO4, the reduction mechanism c all 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 wer e 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 stat e, restrictions based on solubility are eliminated and dissolution of adher ed solid becomes very rapid. This stage of the dissolution process R:BS stu died by cyclic voltammetry, single- and double-potential-step methods, chro nocoulometry and microgravimetry, and again has been modelled. Q 2001 Elsev ier Science B.V. All rights reserved.