Electron-transfer reactions of organic compounds in highly concentrated (1-10 M) redox solutions are investigated. Extensive use is made of microelectrode techniques to obtain quantitative transport and kinetics data in solutions containing molar-level concentrations of electroactive species. Initial studies focus on several recently identified mass-transport phenomena, including accelerated transport rates resulting from homogeneous electron-transfer reactions. In addition to microelectrode techniques, phase-measurement interference microscopy and quartz-crystal microbalance methods are used to measure physical parameters of the electrochemical depletion layer. Other emphases include developing a detailed description of the dependence of heterogeneous electron-transfer rate constants on concentration and the investigation of the dependence of coupled chemical reactions (including catalytic reactions) on local electric fields; electrochemical reduction of ketones is studied in detail to determine the effects of high electric fields on reaction selectivity. Commercial electrosynthetic processes are usually run in highly concentrated solutions since these give a better energy efficiency and higher throughput than do dilute solutions, but almost all laboratory electrochemistry is done in dilute solutions where variables are more easily isolated and interpreted. By creating a fundamental framework for the properties of concentrated solutions, this work will make feasible a rational scale-up paradigm for electrochemical processes. This is an award under the joint Initiative on Electrochemical Synthesis sponsored by the National Science Foundation and the Electric Power Research Institute.
