Mechanism of Ammonium Thiocyanate Decomposition Driven by Electrolytic Hydrogen Charging

Abstract

In this study, the mechanism of pH decrease in an electrolytic solution containing ammonium thiocyanate (NH₄SCN) during electrolytic hydrogen charging was elucidated. The pH of an electrolytic solution containing NH₄SCN decreases during hydrogen charging, which is caused by the formation of sulfate ions from the oxidative decomposition reaction of thiocyanate ions (SCN⁻) on a Ti-Pt anode. The suppression of pH decrease using a cation-exchange-resin-coated IrO₂ electrode, which has a lower probability of decomposing NH₄SCN than a Ti-Pt anode, was investigated to develop a method for controlling the pH decrease in an electrolytic solution containing NH₄SCN during electrolytic hydrogen charging. Specifically, the use of a cation-exchange-resin-coated IrO₂ electrode suppresses the decrease in the pH of the electrolytic solution.

 

This Paper was Originally Published in Japanese in Zairyo-to-Kankyo 74 (2025) 26–32. All figures and captions are slightly modified. Also the chemical formula (5), (6) and unit are corrected.

Anodic reactions of Ti-Pt and cation-exchange-resin-coated IrO₂. Anodic polarization curves of (a) Ti-Pt and (c) cation-exchange-resin-coated IrO₂ in Na₂SO₄ aqueous solution.