Voltammetric Response of Zeolite‐Modified Electrodes

Abstract

As a prelude to using zeolites as supports for electrocatalysts, the voltammetric behavior of various analytes was examined at zeolite‐modified electrodes in aqueous solution. The following parameters were studied: preparation and characterization of electrodes, ability to concentrate or exclude analytes from dilute solution, linearity of response to concentration of analytes in solution, selectivity toward analytes of various sizes and charges, and the role of electrolyte cations in determining the response. The following analytes were used: methyl viologen dication (N,N′‐dimethyl‐4,4′bipyridyl), heptyl viologen, hexammineruthenium (III), hexacyanoferrate (III), and copper (II). Zeolites mixed with carbon paste gave more reproducible and robust electrodes than did films of zeolite/polystyrene on platinum or glassy carbon electrodes. Electrodes modified with zeolite Y concentrated methyl viologen, hexammineruthenium (III), and Cu(II) from dilute solution (0.1–10 mM), and cyclic voltammetric peak current was linear as a function of solution concentration after an equilibration period of 1h. Ferricyanide and heptyl viologen were excluded from the zeolite based on charge and size, respectively, and were therefore not concentrated from solution. The smaller pore zeolite A accommodated only Cu(II). Selectivity and competition among pairs of analytes were also examined. The peak current in cyclic voltammetry was also correlated with the mobility of electrolyte cations within the zeolite matrix, based on their charge, and their size relative to the size of the zeolite channels. Enhancement factors (defined as peak current at a modified electrode divided by that at an unmodified electrode) reached values in the range of 50, despite the loss of active surface area of the electrode caused by the modification.

The Electrochemical Behavior of Iron(III) Incorporated in Zeolite Y-Modified Electrode and the Catalytic Oxidation of Ascorbic Acid

“…It can be seen from Figure 2 that the response current of ferricaferrous increases as the hydrated radius of the electrolyte co-ion decreases. This is in agreement with the literature [3,12]. The experimental results of Figure 2 indicate that the electroactive species existing in the zeolite are exchanged with the electrolyte co-ions, and then escape from the zeolite to be reduced on the interface of zeoliteelectrode-solution.…”

“…The voltammetric experiments illustrate that the optimum proportion of zeolite and graphite powder is 1 : 1. This conclusion was similar to that by Shaw [3]. From another discussion [27], it is known that the kind and concentration of the supporting electrolyte had obvious in¯uences on the electron transfer of ZME, so the effect of the supporting electrolytes was estimated in our experiment.…”

“…These two experimental conclusions illustrate that the electron transfer step occurs at the zeolite-electrodesolution interface after ion exchange between the electroactive species and the cations in solution. The transfer mechanism is in conformity with the extrazeolite electron transfer mechanism actioned by Shaw et al [3].…”

Oxidative bromination and oxidation of organic substrates catalyzed by bis[2,2'‐hydroxyphenylbenzimidazole]Fe(III) complex entrapped in zeolite‐Y cavity

“…). According to previous reports, if electron transfer occurs between the species within the cavities of zeolite, peak intensity increases without any prominent shift in peak positions, termed an intra‐zeolite mechanism …”

Voltammetric copper(II) determination with a montmorillonite-modified carbon paste electrode

“…A carbon paste electrode (CPE) modified with zeolite was tested for the determination of Cu(II) [5,6], a linear voltammetric response was obtained from 10\ to 10\ mol/l [5]. Ogorevc et al showed the latest use of a vermiculite modified CPE which exhibited a detection limit of 5;10\ mol/l Cu [7].…”