Research on Hydrogen Production by Electrochemical Decomposition of HI x Solution

The electrochemical decomposition of HI x solution presents a promising alternative to overcome the challenges associated with HI thermal decomposition in the sulfur–iodine (S-I) cycle. In this study, constant current electrolysis and LSV tests were carried out for HI x solution using an H-type electrolyzer at different current densities and anode solution compositions. The results showed that during the process of HI electrolysis, the dominant factor of voltage variation gradually changed from electrochemical polarization to ohmic polarization as the current density increased. When the I 2 concentration in the HI solution approached saturation, a voltage step occurred in the constant current electrolysis, reaching a maximum amplitude of 127.69%. The analysis indicated that the voltage step was related to the I 2 deposition on the electrode and PEM, which led to the simultaneous increase in activation polarization and ohmic polarization overpotential. The increase in I 2 concentration decreased the limiting diffusion current density; I 2 supersaturation led to the formation of an insoluble iodine film on the electrode surface, ultimately terminating the electrochemical reaction. This study provides guidance for the development of HI x solution electrolysis technology for hydrogen production.