Formation of nickel hydrides by hydrogen evolution in alkaline media: effect of temperature

The effect of temperature on the hydrogenation of sintered Ni by the hydrogen evolution reaction (her) in 0.6 M K2CO3H2O electrolyte was investigated in the range 25-95°C. At 25°C, hydrogenation leads to the formation of three different species, provisionally identified as b-Ni-, hexagonal-Ni- and a-Ni-hydride phases, based on their respective redox potentials and thermostability. Their penetration into the metal ranged from a few tens to a few hundred monolayers. Above room temperature, the overall efficiency and penetration of Ni hydrogenation increased significantly. Furthermore, there is definite evidence that, at T]65°C, the b-Ni-hydride phase evolves into new Ni-hydrogen species of higher thermal stability, regarding which there is no previous knowledge. The results of electrolytic Ni deuteration by electrolysis of K2CO3D2O conformed to those obtained in light water. © 1998 Elsevier Science S.A. All rights reserved.