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

The effect of high intercrystalline content on hydrogen activity and t ransport in nickel has been studied. The electrocatalytic behavior of Ni has been determined in low concentration alkaline media with refere nce to the hydrogen evolution reaction (HER) by potentiostatic methods . The effect of structure on the Tafel parameters has been examined. N anocrystalline Ni was found to exhibit enhanced electrocatalytic activ ity relative to cold worked, fine grained and fully annealed Ni electr odes. A supplementary investigation into the transport behavior of hyd rogen in Ni was studied in order to determine hydrogen diffusivities a nd 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: nanocrysta lline, fine grained and single crystal structures. The apparent concen tration of hydrogen determined from permeation transients is dramatica lly increased in nanocrystalline Ni.