THE INFLUENCE OF INTERCRYSTALLINE DEFECTS ON HYDROGEN ACTIVITY AND TRANSPORT IN NICKEL

The effect of high intercrystalline content on hydrogen activity and transport in nickel has been studied. The electrocatalytic behavior of Ni has been determined in low concentration alkaline media with reference to the hydrogen evolution reaction (HER) by potentiostatic methods. The effect of structure on the Tafel parameters has been examined. Nanocrystalline Ni was found to exhibit enhanced electrocatalytic activity relative to cold worked, fine grained and fully annealed Ni electrodes. A supplementary investigation into the transport behavior of hydrogen in Ni was studied in order to determine hydrogen diffusivities and apparent concentrations as a function of intercrystalline content. Electrolytic charging of hydrogen was performed on Ni bi-electrodes in an electrochemical double cell. Detection of permeated hydrogen in Ni membranes of identical thickness is observed in the order: nanocrystalline, fine grained and single crystal structures. The apparent concentration of hydrogen determined from permeation transients is dramatically increased in nanocrystalline Ni.