Non-aqueous electrochemical studies at a high temperature channel flow cell heated by radio frequency radiation

Abstract

The effect of applied temperature was studied on various non-aqueous one- and two-electron systems of ferrocene, tris(4-bromophenyl)amine and N, N, N′, N′-tetramethyl-1,4-phenylenediamine in acetonitrile solvent at both radio frequency channel cell (RFCC) and microdisk electrode apparatus. Experimentally obtained diffusion coefficients ( D c) and activation energies ( E A) for both RFCC and microelectrode experiments are in excellent agreement with each other and published data. Analysis of the data in terms of the Stokes–Einstein equation is also presented. This expands on previous work done in this area to incorporate not only solvent-based systems in addition to simple aqueous electrochemistry, but also more mechanistically complex electrode processes with coupled homogeneous kinetics such as ECE reactions. The application of the RFCC as a tool for mechanistic studies is discussed with the investigation of the well characterised ECE reaction of m-iodo-nitrobenzene in acetonitrile, giving a value of 80±5 kJ mol −1 for the activation energy of the rate constant for the decomposition of the m-iodo-nitrobenzene radical anion. This represents, to the authors' knowledge, the first example of a quantitative, fully modelled investigation of a mechanistically complex electrochemical process at a locally heated electrode.