Electrochemistry in the absence of a contacting electrolyte solution, using ionically conductive polymers of perflurosulfonic acid (Nafion) coatings and membranes, is reviewed. Various types of reference electrodes, including a polymer Ag/AgCl electrode and Ag directly sputtered on the Nafion membrane, were used. Voltammetry of model redox couples, such as potassium ferricyanide and various ferrocenes, was conducted in a solid-state configuration and compared to that obtained in aqueous solution. Dioxygen reduction catalyzed by an electropolymerized metalloporphyrin with a Nafion film serving as polyelectrolyte, shows similar features as observed using the modified electrode concept. However, catalysis of O2 reduction in the presence of the cobalt (II) ammoniacal complex is more effective in the solid-state configuration. Dioxygen reduction in this case occurs 800 mV more positive than obtained in aqueous solution. New applications of solid-state electrochemistry in the fields of electrodeposition, monitoring of acidic gases and electrocatalysis are also reported.
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