Electrochemical studies of molten sulfates in LiCl-KCl-Na2SO4 at 700 °C

The electrochemical reduction behavior of molten Na2SO4 was investigated at 700 °C in LiCl-KCl-Na2SO4 (5-15 mol%) electrolyte under two different gaseous atmospheres of inert argon and oxidizing O2-0.1% SO2. Sulfate ions (SO42-) were directly reduced into sulfur (S) and sulfide (S2-) ions at large negative overpotentials in both gaseous atmospheres. During the transition from inert to oxidizing atmosphere, open circuit potentials of a platinum electrode (vs. Ag/Ag+) were shifted in the positive direction by more than 0.60 V, implying the presence of stronger oxidants which can be coupled with the metal oxidation reactions during the hot corrosion processes.