Electrochemistry in Fused Alkali Thiocyanates

Abstract

Detailed polarographic and chronopotentiometric investigations were conducted in molten potassium thiocyanate and the eutectic mixture of 70 mole % and 30 mole % . Between 150° and 325°C, electrochemical oxidation occurred at a potential of +0.25v (vs. ) to produce thiocyanogen, , which polymerizes to parathiocyanogen, . At the cathode, the ion was reduced to sulfide and cyanide ions at a potential of −1.75v. At higher potentials, the half‐wave potentials were −2.35v for Na+ and −2.92v for K+. In a continuing series of fractional factorial experiments with laboratory prototype pill cells (laminar, 1–3 mm thick, 1 cm in diameter), thiocyanate electrolytes were used with a variety of alkali metal anodes and various cathode materials such as transition metal oxides, silver salts, and organic nitro compounds. At current densities approaching 100 ma/cm2, closed‐circuit voltages ranged from 1.50 to 2.50v for at least 5 min. At a temperature of 200°C, this performance is approximately equivalent to that of the best previous thermal cells in operating at 450°C.