Hydrogen Evolution and Surface Oxidation of Nickel Electrodes in Alkaline Solution

The electrochemical processes which occur on nickel electrodes in during a slow‐speed anodic potential sweep between −300 and +1500 mv were studied. Tafel plots for hydrogen evolution were determined under different conditions, and the impedance was measured at 100 cps as a function of potential. The results are interpreted in terms of the adsorbed species. It is confirmed that hydrogen evolution between −300 and −100 mv is controlled by the discharge step of water molecules (Volmer reaction) and that the coverage with electrochemically active hydrogen atoms is small in this region. Prior to the formation of an adsorbed layer of OH‐radicals appears to be formed.