Surface Evolution of Ni Electrode Under Cathodic Polarization in Acidic Solution

The surface morphology and structure of nickel cathode is closely related to its service performance and stability for water electrolysis applications. However, the surface evolution of nickel under cathodic polarization has not been systematically studied. In this work, we investigated the morphology evolution of the Ni electrode under cathodic polarization by altering the current density, temperature and composition of electrolyte. A corrosion rate of less than 0.0054 mm a−1 is observed under cathodic polarization at 0.2 mA cm−2. Uniform corrosion appears at low current density (0.2–2 mA cm−2) while serious pitting at high current density (20–200 mA cm−2). The corrosion preferentially takes place at the surface flaws, scratches and cavities. The cathodic corrosion is due to the uneven distribution of the surface potential between the plane and the depression part of the electrode. The mechanism is further confirmed by finite element simulation. The obtained result may provide reference for the design and application of various Ni-based cathodes.