Mediated oxidations in a sol-gel-based solid-state cell with isolated counter and working electrodes

Abstract

A solid-state cell consisting of two adjacent layers of silica prepared from tetraethyl orthosilicate (TEOS) sols was developed for performing controlled potential electrolysis with isolated counter and working electrodes. The porous silica layer in contact with the working electrode was loaded with an electron-transfer mediator which increased the effective population of redox sites, thereby providing electrolysis efficiency in a system with limited physical diffusion. The mediator, a mixed-valence ruthenium oxide polymer, was doped into one silica layer by including its precursors, RuCl3 and K4Ru(CN)6, in the corresponding sol. The test substances were doped in the same manner. The second silica layer was prepared from undoped TEOS. A comparison of cyclic voltammetry in the solid-state cell to that in aqueous solution established the integrity of the bilayer cell. In agreement with aqueous solution experiments, the oxidation of glutathione, when promoted by Ru(VI), yielded its cysteic acid analogue.