Identification of processes that occur after reduction and dissolution of C60 adhered to gold, glassy carbon, and platinum electrodes placed in acetonitrile (electrolyte) solution

Microcrystals of C-60(solid) may be adhered to glassy carbon, gold and platinum electrodes. When the electrodes containing C-60(solid) are placed in acetonitrile (0.10 mol L-1 Bu4NClO4) and the potential is scanned or stepped to significantly negative potentials, very fast dissolution processes of the kind C-60(solid) + ne(-) -->(fast) C-60(n-)(soln) (n = 3-5) occur. In contrast, one- and two-electron reductions only leas to a minor level of dissolution of C-60(-) and C-60(2-). Electrochemical quartz-crystal microbalance studies on gold electrodes revealed that C-60(2-)(solid) and C-60(-)(solid) are intermediates in the n greater than or equal to 3 reduction-dissolution processes and that a range of adsorption and precipitation steps occur when the dissolved material is oxidized back to C-60(solid). The exact details of the mechanism of the process that occur after reduction of C-60(solid) to dissolved C-60(n-)(soln) (n = 3-5) under conditions of cyclic voltammetry depend on the scan rates, electrode material, and switching potentials employed . However, under carefully chosen conditions at a glassy carbon electrode, reaction schemes of the kind C-60(solid) + 5e(-) --> C-60(5-)(soln) and C-60(5-)(soln) reversible arrow(+e-)(-e-) C-60(4-)(soln) reversible arrow(+e-)(-e-) C-60(2-)(w/ad) reversible arrow(+e-)(-e-) C-60(-) (w/ad) are operative, where the symbol "w/ad" represents weak adsorption. However strength of adsorption increases on the order of C-60(-) much greater than C-60(2-) > C-60(3-) > C-60(4-) > C-60(5-), so that strong adsorption and even solid formation occur under other conditions and only fully surface confined C-60(solid) could be detected. The relationship between dissolution, adsorption, and surface attachment processes that accompany the voltammetry of C-60 has been identified.