Abstract
Energy efficiency losses at nickel cathodes in water electrolysis systems using aqueous potassium hydroxide electrolyte were discussed by the authors in a previous study (1). Four mechanisms were proposed to explain the cathode voltage increase with time responsible for the loss of efficiency, three of which were contraindicated. Preliminary evidence to support the remaining mechanism, absorption of atomic hydrogen by the cathode, was included in that study. This paper presents the results of an additional study to investigate the role of absorbed hydrogen. Absorption was confirmed and subsequent diffusion measured by the Devanathan cell method. A strong correlation of absorption/diffusion rate with hydrogen evolution kinetics was found. The formation of a β‐nickel hydride layer at the cathode surface is believed to be the cause of the voltage‐time phenomenon.