A New Method of Studying Ion Transfer at Liquid|Liquid Phase Boundaries Using a Carbon Nanotube Paste Electrode with a Redox Active Binder

Abstract

We report a new method for the study of voltammetric processes at liquid vertical bar liquid interfaces, namely that of using a redox active organic oil as the binder in a carbon nanotube (CNT) paste electrode. Specifically we report voltarnmetry at the,liqui vertical bar liquid interface studied at a N,N-didodecyl-N',N'-diethylphenylenediamine (DDPD, as binder) CNT paste electrode immersed in aqueous electrolytes containing potassium salts of various anions (AsF6-, PF6_, ClO4-, SCN-, I-, NO3, Br-, Cl-, F-, and SO42-). Ion transfer across the liquid vertical bar liquid interface occurs to maintain electroneutrality upon oxidation of the DDPD, the direction of which, and the subsequent effect upon the observed voltammetric response, is found to be driven by the relative hydrophobicity of the ions involved. This method of studying liquid vertical bar liquid interfaces offers significant advantages, not least with regard to ease of electrode fabrication and cleaning and the formation of multiple three-phase boundaries (at which any voltarnmetry must occur) due to the structure of the DDPD-CNT paste vertical bar aqueous electrolyte interface.