SILVER ION-EXCHANGED ZEOLITE MODIFIED ELECTRODES - OBSERVATION OF ELECTROCHEMICALLY DISTINCT SILVER IONS

In this paper the electrochemical response of electrodes modified with silver ion exchanged Y type zeolites is examined. The cyclic voltammograms for the fully exchanged materials resemble closely those observed previously for silver mordenite zeolites. At low exchange levels (<10%, i.e., <5.6 silver ions per unit cell) cathodic linear sweep voltammetry indicates the presence of two electrochemically distinct silver ions. These are shown to be slowly interconverting by measurements recorded as a function of both scan rate and temperature. Of these two species, the more difficult to reduce apparently migrates from its site following electrochemical reduction. The population of this site reaches a maximum at low exchange levels, whereupon further loading of the zeolite with silver occurs in other sites. The relative population of these two sites is also sensitive to cocation. The behavior of the cathodic waves as a function of concentration and cocations that are known to displace silver ions from the hexagonal prisms is discussed. These data show that the two cathodic waves observed at low silver concentrations are related to occupancy of sites I and I′. © 1990 American Chemical Society.