Electrochemistry of polyoxometalates immobilized in ion exchange polymer films

Abstract
The polyoxometalate ions PMo12O403−, PW12O403−, and SiW12O404−are incorporated in polymeric ruthenium(II)(vinyl)bipyridine (poly-Ru(vbpy)32+) 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 charge in poly-Ru(vbpy)32+. An investigation of the effect of environmental conditions on electrochemical behavior reveals that the first two one-electron reduction waves of SiW12O404−coalesce into a single two-electron reaction and those of PW12O403−shift significantly in potential upon a change from pure aqueous to 50(v/v)% dioxane/water 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(vinyl)pyridine and poly-Ru(vbpy)32+films from dioxane–water solvent results in differences in electrochemical behavior. Polyoxometalate anions incorporated in poly-Ru(vbpy)32+films catalyze the electrochemical reduction of hydrogen ion. Keywords: polyoxometalate, electrochemistry, poly-Ru(vbpy)32+, electrocatalysis, immobilization.

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