Electrochemical Behavior of Nickel in Acidic Sulfate Electrolytes,

The electrochemical behaviour of Nickel in sulphuric acid
electrolytes was studied by various electrochemical means. Under
cathodic polarization, Nickel forms metastable hydrides under
cathodic charging; the successive egress of hydrogen is controlled
by solid state diffusion of hydrogen atoms. The nature of these
hydrides evolves with electrochemical aging of the samples, as
judged by their electrochemical signature. The nature of the
(hydro)oxides formed during anodic polarization also evolves with
aging. Anodic polarization and investigation of electrochemical
oscillations in the transpassive region show that defect states which
constitute preferred dissolution sites assume a wider energy range
with increasing aging, indicating a high degree of inhomogeneity
of the surface. The catalytic activity of Nickel increases after aging
under both cathodic and anodic conditions, due to the formation of
an inhomogeneous surface