Electrochemistry of metalloporphyrins and viologens at zeolite Y-modified electrodes: evidence for electron trapping by monomolecular porphyrin layers

Abstract

Cyclic voltammetric data are presented for electrodes coated with zeolite Y powder containing porphyrins and viologens. Half-wave potentials for viologen cations (methylviologen, benzylviologen, or N,N'-( 1,3-propenyl)-2,2'-bipyridinium) do not change significantly when they are exchanged into zeolite Y, whereas the reduction potentials for cobalt and zinc tetrakis(7V-methyl-4-pyridyl)porphyrins shift (relative to aqueous solution) by +200 mV. When a viologen cation is ion exchanged into the bulk of the zeolite, and cobalt tetrakis(7V-methyl-4-pyridyl)porphyrin is adsorbed onto its outer surface in monolayer quantities, current rectification and charge trapping reactions are observed. The charge "untrapping" reactions are similar to those previously observed at redox polymer bilayer electrodes and are attributed to a kinetically fast cross reaction between doubly reduced viologens inside the zeolite and cobalt(II) porphyrin on the outer surface. Rotating disk experiments show that the porphyrin monolayer effectively seals up the zeolite against exchange of encapsulated viologens with solution-phase cations.

The use of NaX zeolite as a template to obtain a mono-atomic pt dispersion by impregnation with Pt(II) acetylacetonate/acetone solution

“…[21][22][23] Quite recently, zeolites were used as templates to produce metal particle of uniform, sub-nanometer dimensions for electrocatalysis purposes. For instance, Coker et al 11,24 incorporated Pt nanoclusters in NaX zeolite (faujasite type) by the ion-exchange technique, and, upon zeolite dissolution, transferred them to a carbon support to obtain Pt/C electrocatalysts.…”

Synthèse critique de la caractérisation électrochimique de zéolithes et d'aluminophosphates chimiquement modifiés

“…On peut citer comme exemple le cas de la détection ampérométrique de glucose (27) ou de dopamine, méthylviologène, Ag + et Cu 2+ (29) avec une électrode à pâte de carbone contenant la zéolithe Y et la glucose oxydase ou les zéolithes A, X et Y, respectivement. La possibilité d'incorporer dans la zéolithe des espèces électroactives a conduit à la conception de matériaux moléculaires élaborés dont l'application la plus élégante est l'étude de transferts électroniques orientés (31)(32)(33). Dans le domaine de l'électrocatalyse, l'électrode composite à base de zéolithe témoigne également d'un potentiel indéniable (34)(35)(36)(37)(38), comme cela a été montré dans le cas de la réduction sélective de bromure de benzyle, par rapport au bromure de triphénylméthyle, par le complexe zéro valent du nickel bis-bipyridine encapsulé dans la zéolithe Y (34).…”

Electrochemically controlled ion exchange: Copper ion exchange with sodium zeolite Y

“…Zeolites are used to modify electrode surfaces and so imbue some of their properties including: shape [16], size [17,18], site [19,20] and charge [21] selectivities, improved physical and chemical stabilities [22], and hydrophilic character [23]. This has led to promising applications in the areas of: electrosynthesis [24], electroanalysis [22,25] and electrocatalysis [16].…”