Mixed Ionic / Electronic Conductivity of Electrolyte-Modified Carbon/Zirconia Composites

Abstract

A recently developed method for independently obtaining electronic and ionic contributions to electrical conductivity was used to study conductivity in thin-film samples of carbon/zirconia nanocomposite materials for which molecular and polymer electrolytes were covalently grafted onto the carbon/zirconia particle surfaces. The method relies upon careful control of the nature of the contact between the sample and the current-carrying electrodes. Electronic conductivities are derived from currents obtained when using electronically-conductive glassy carbon electrodes to contact the sample, whereas ionic conductivities are derived from currents obtained when using ionically-conductive Nafion electrodes to contact the sample. Carbon / zirconia samples were prepared from zirconia sol precursors combined with RF carbon aerogels and also with carbon black to produce carbon containing integrated zirconia. Solution-phase treatment with molecular electrolytes containing organo-phosphonate groups resulted in electrolyte attachment via zirconia-phosphonate binding. Thin-film samples of the resulting electrolytes were prepared and their mixed electronic and ionic conductivity studied as functions of temperature and relative humidity