Anodic behavior of hydrogenated nickel in sodium hydroxide solutions

The anodic behavior of hydrogenated nickel in sodium hydroxide solutions (0.01 to 1 N) is studied with the use of cyclic voltammetry, chronocoulometry, and chronoammetry. At the anodic dissolution of an alpha-phase (Ni-0.03 at. % H), the ionization of hydrogen is limited by its diffusion in the solid phase. The diffusion coefficient of hydrogen D-H and the apparent thickness delta(H) of the nickel layer depleted of hydrogen are calculated to be D-H = 1 x 10(-8) +/- 2 x 10(-9) cm(2)/s and delta(H) = 1.9 x 10(-4) cm. The D-H value is independent of the alkali concentration, while delta(H) is independent of the duration and potential of hydrogenation. The cyclic voltammetry experiments have shown that the diffusion is unaffected by the possible formation of nickel oxides.