Electrochemical behavior of a graphite anode in fluorosulfonic acid at −78 °C

Abstract

Electrochemical oxidation of fluorosulfate ion (SO 3F −) on a graphite anode gives peroxydisulfuryl difluoride (S 2O 6F 2) at − 78 °C in KSO 3F/HSO 3F solution. Continuous electrolysis finally results in a potential jump of the graphite anode, which is quite similar to the anode effect found in the molten KF·2HF electrolysis to produce elemental fluorine. The formation of a metallic blue graphite fluorosulfate, C x SO 3F · n(HSO 3F), is mainly achieved by the chemical reaction of graphite with S 2O 6F 2 as the electrolyte solution is warmed up to room temperature after the electrolysis.