Abstract
Zeolites NaA and NaY were coated onto platinum electrodes. The effects of channel diameter in the zeolites, size of electrolyte cation, solvent, and solubility of methyl viologen on electron transfer and ion-exchange behavior were studied. When exposed to electrolyte solutions containing methyl viologen ( N, N′-dimethyl-4,4′-bipyridyl dichloride), ion-exchange of the viologen occured into zeolite Y (large pores) but not into zeolite A (small pores). In water, electrochemistry of methyl viologen in NaY zeolite on the electrode surface resembled that of methyl viologen at clean platinum. When the zeolite-coated electrode was used in acetonitrile, however, cyclic voltammetric peak shapes changed dramatically. Generation of the neutral viologen species by subsequent reduction of the methyl viologen cation radical appeared to lead to a comproportionation reaction of the neutral species with the dication remaining in the zeolite, to regenerate the cation radical. The electrochemical behavior of methyl viologen exchanged into NaY zeolite in acetonitrile depended on the size of electrolyte cations. Electron transfer and loss of methyl viologen vy leaching were fast in the presence of lithium perchlorate solution and slow in tetraethylammonium and tetrabutylyammonium perchlorate solutions. A mixed electrolyte (tetraheptylammonium bromide + lithium perchlorate) solution prevented solubility of methyl viologen while (facilitating charge transfer.
Published Version
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