Electrochemical Study of the Nickel-Hydrogen System

A study has been made to determine the potential of a mixed nickel‐hydrogen electrode containing up to about 0.7 H atoms per Ni atom. Nickel layers electrodeposited on copper foils were charged cathodically in sulfuric acid solutions containing thiourea or selenium dioxide as catalytic poisons of the hydrogen recombination reaction. The electrode potential of nickel charged with hydrogen and kinetics of decomposition of the hydride phase were studied as functions of time of hydrogen desorption and p H of the electrolyte. The results show that the nickel‐hydrogen system behaves electrochemically like the palladium‐ hydrogen system. The open‐circuit potential of , i.e. , of a nickel‐hydrogen electrode presumably containing a mixture of alpha and beta phases, is a linear function of p H, with a value approximately 0.13v less noble than that of the hydrogen electrode. The desorption rate of hydrogen from Ni‐H depends on the p H.