Mechanical and electrochemical characteristics of composites of wired glucose oxidase and hydrophilic graphite

In glucose electro-oxidation catalyzing redox hydrogels, through which reaction centers of glucose oxidase are electrically connected (wired) to electrodes, electrons diffuse by their transfer between colliding redox centers. The colliding centers are tethered to the hydrated redox polymer. The mobility of the polymer segments and the diffusivity of electrons increase upon hydration and swelling, but the gels lose their strength and are readily sheared off when mechanically stressed. As a result, gels that are not highly cross-linked are soft, but the upper kinetic limit of their glucose electro-oxidation current density is high, similar to 1.2 mA cm(-2). Gels that are highly cross-linked are mechanically strong, but the upper kinetic limit of their current density is only similar to 0.4 mA cm(-2). We show here that composites of >90 wt % hydrophylized graphite particles and <10 wt % highly cross-linked, glucose-oxidase containing redox hydrogels are mechanically strong, yet their kinetically limited current density is high, 1.6 mA cm-l (C) 2000 The Electrochemical Society. S0013-4651(00)03-007-X. All rights reserved.