Methods for Determining Oxygen Overvoltage and Anode Poisoning Over Time at Iron-Group Metals under High Current Densities in Alkaline Water Electrolysis

摘要

Determination of oxygen overvoltage ( . s ) is complicated by high current densities under alkaline water electrolysis. Therefore, it is desirable to develop method for advanced control of oxygen overvoltage. Here, we show that the modified rotating anode method offers a number of advantages for determination of oxygen overvoltage in alkaline water electrolysis under high current densities. These include elimination of the gas (oxygen) shielding anode, the electrolyte gas filling near anode, and concentrating polarization. The mechanism of the anode material poisoning in time has been further developed by us based on the highest metal oxide surface concentration increased in time. Specifically, in a case of Ni anode: Ni 2 O 3 NiO 2 at the current density, i = (0.1-3.0) A/cm 2 . For Ni and Co anode: NiO 2 (CoO 2 ) NiO 3 (CoO 3 ) at i (3.0-10.0) A/cm 2 . It has been shown that the oxygen overvoltage on Ni is higher compared to Co or Fe anode, and there are no significant differences between oxygen overvoltage on Co and Fe: . s (Ni) .. s (Co ) .. s (Fe). The difference in oxygen overvoltage between different metals increases with the increase in current density. Recommendations on using galvanic alloy composed of Co and Ni are given to assure the cost effectiveness of the galvanic system and better resistance to corrosion .