Absorption of hydrogen in reduced nickel oxide

By repeated oxidation and reduction of nickel in alkaline solution an oxide film is formed on nickel which cannot be reduced further. In this film hydrogen is absorbed during cathodic polarization. The absorbed hydrogen is manifest in the voltammogram as an anodic peak before the Ni(OH)₂ peak. This was proved by H-diffusion experiments through nickel foils. From experiments with Ni electrodes covered with- or-Ni(OH)₂ films, it can be concluded that the reduced nickel oxide layer on nickel is most likely a-Ni(OH)₂ layer.