Electrochemistry of polyoxometalates immobilized in ion exchange polymer films

Abstract

Abstract:The polyoxometalate ions P M O , ,~, ,~~, PW~,O,~-, and S~W,,O,;-are incorporated in polymeric ruthenium(II)(vinyl)bipyridine (poly-~u(vbpy),2+) films from aqueous and dioxane-water electrolytes. Despite their large mass the ions exist as freely diffusing species that compensate for up to 30% of the chage in poly~u ( v b~~)~~~. An investigation of the effect of environmental conditions on electrochemical behavior reveals that the first two one-electron reduction waves of s~w,,o,,~-coalesce into a single two-electron reaction and those of PW,,O,,,-shift significantly in potential upon a change from pure aqueous to 50(v/v)% dioxanelwater solvent. The observation is attributed to destabilization of the one-electron reaction products as the solvent is enriched is dioxane. Incorporation of polyoxometalates in protonated poly(viny1)pyridine and poly~u ( v b~~) ,~~ films from dioxane-water solvent results in differences in electrochemical behavior. Polyoxometalate anions incorporated in poly-~u(vbpy)3'f films catalyze the electrochemical reduction of hydrogen ion.Key words: polyoxometalate, electrochemistry, poly-~u(vbpy)32+, electrocatalysis, immobilization.RCsumC : On a incorporC les ions polyoxomCtallates PMO,~~,,", PW,,~,," et Siwl,O4,4-dans des films polymCriques de mthCnium(II)(vinyl)bipyridine (poly-~u(vbpy),") 2 partir d'Clectrolytes en solutions dans l'eau ou dans un mClange eau~lioxane. MalgrC leurs masses importantes, les ions existent sous la forme d'espkces qui diffusent librement et ils peuvent compenser Clectrostatiquement jusqu'i 30% de la chage du poly-~u(vbpy)33+. Une Ctude de l'effet des conditions environnementales sur le comportement Clectrochimique rCvkle que le potentiel des deux premikres vagues de rCduction du s~w ,~o , ,~-par un Clectron est fortement modifiC lorsqu'on passe de I'eau pure i un mClange de solvants form6 i 50% (vlv) de dioxaneleau. On attribue ces observations i la destabilisation des produits de rCduction par un Clectron lorsqu'on enrichit le solvant en dioxane. L'incorporation de polyoxomCtallates dans des films de poly(viny1)pyridine ou de poly~u ( v b~~) ,~+ protonCs B partir de solvants mixtes dioxane-eau provoque des diffkrences dans le comportement Clectrochimique. Les anions polyoxomCtallates incorporCs dans les films de poly-~u(vbpy)33f catalysent la rCduction Clectrochimique de l'ion hydrogkne.

Electrochemical Properties of Polyoxometalate (H3PMo12O40)-Functionalized Graphitic Carbon Nitride (g-C3N4)

“…The current response increased with the increase of the scan rate (Fig. 4c), and similar curves with three pairs of redox peaks were observed at all scan rates, with no obvious distortion [25]. This observation indicates sufficient electron transfer from the PMo 12 cluster to the electrode in all subsequent redox steps.…”

Electrochemical Preparation and Characterization of Silicotungstic Heteropolyanion Monolayer Electrostatically Linked Aminophenyl on Carbon Electrode Surface

“…The attachment of the Keggin [XM 12 O 40 ] p - or Dawson [X 2 M 18 O 62 ] q - parent structure has been largely explored: (i) heteropolyanions are adsorbed on carbon electrode, − which often involves vigorous oxidation processes resulting in the formation of oxygenated functional group on carbon surface, whose nature and number are difficult to identify and control; (ii) heteropolyanions as a dopant are immobilized into polymer films − (e.g., polypyrrole, polyaniline, polythiophene, and their derivatives). However, in some cases, the polymer environment affects the electrochemical behavior and the electrocatalytic properties of the immobilized heteropolyanions. ,,, (iii) Heteropolyanions are electrodeposited on metal electrode. − Despite the amount of literature the many methods used for the attachment of heteropolyanions on substrate surface, little study has been reported on how to design a well-organized and structure-controlled molecular assemblies of heteropolyanion, while maintaining and/or enhancing their above beneficial properties. Recently, several composite film containing heteropolyanion modified electrodes have been prepared by several groups. − These techniques were shown to be rapid and simple to obtain organized molecular assemblies experimentally with precise control of layer composition and thickness.…”

“…5 To take advantage of their specific properties observed in solution, the attachment of such species onto electrode surfaces is of great interest. The attachment of the Keggin [XM 12 O 40 ] por Dawson [X 2 M 18 O 62 ] qparent structure has been largely explored: (i) heteropolyanions are adsorbed on carbon electrode, [6][7][8] which often involves vigorous oxidation processes resulting in the formation of oxygenated functional group on carbon surface, whose nature and number are difficult to identify and control; (ii) heteropolyanions as a dopant are immobilized into polymer films [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] (e.g., polypyrrole, polyaniline, polythiophene, and their derivatives). However, in some cases, the polymer environment affects the electrochemical behavior and the electrocatalytic properties of the immobilized heteropolyanions.…”

Composite microspheres with PAM microgel core and polymerisable surfactant/polyoxometalate complexes shell

“…The immobilization of catalytically active species onto solid supports can solve the catalyst recovery and recycle. As a result, water-insoluble polyoxotungstates including insoluble bulk materials, 4,8,9 impregnation of homogeneous catalysts onto inert solid supports metal hydroxides 7,[10][11][12][13] and polymers, [14][15][16][17][18][19] have been synthesized. Although the catalysts immobilized on insoluble resins and silica gels are suitable for this purpose, they often result in lower catalytic activity compared with their soluble counterparts.…”