The solvent effect on the electrochemical behavior of C-60 films in the presence of alkali-metal cations

The redox behavior of C-60 films was examined in acetonitrile, dimethylformamide, acetone, dimethylsulfoxide and propylene carbonate solutions containing alkali-metal salts as supporting electrolytes. A rapid deterioration in the electrochemical properties of these films is observed during repeated potential cycling. In acetonitrile the change in redox behavior of the film is attributed to the formation of a cation intercalated compound. It is possible that the surface layer of C-60 is wetted by acetonitrile. in dimethylformamide and acetone the C-60(-) salt formed during the charge transfer process is found to be moderately soluble compared with neutral C-60. Dissolution of the fullerene salt is responsible for the deterioration in the electrochemical properties of the C-60 layer in these solvents. In dimethylsulfoxide and propylene carbonate solutions and acetonitrile the formation of intercalated compounds is observed. However, in contrast to acetonitrile, the transport of cations through the C-60 layer determines the rate of electrode processes in dimethylsulfoxide and propylene carbonate. Significant differences in the electrochemical behavior of undoped and doped C-60 layers were also observed. (C) 1997 Elsevier Science S.A.