Mechanism of Ammonium Thiocyanate Decomposition Driven by Electrolytic Hydrogen Charging

Abstract

In this study, the mechanism of the pH decrease of an electrolyte containing ammonium thiocyanate （NH₄SCN） during hydrogen electrolytic charging tests was elucidated. The pH decrease of the electrolyte containing NH₄SCN in the electrolytic charging of hydrogen was caused by the formation of sulfate ions from the oxidative decomposition reaction of thiocyanate ions （SCN^－） on a Pt-based anode.

Furthermore, the suppression effect of an IrO₂-based anode on the pH decrease, having a lower probability to decompose NH₄SCN than a Pt-based anode, was investigated to develop a method for controlling the pH decrease of an NH₄SCN-containing electrolyte during hydrogen electrolytic charging tests. Specifically, using a cation exchange resin-coated IrO₂ electrode, which was found to be highly efficient in oxygen generation, suppressed the pH decrease of the electrolyte as the anode.