Corrosion Behavior and Mechanism of Nickel as a Hydrogen Evolution Electrode Under High Alkalinity and Temperature

This study investigates the hydrogen evolution on nickel (Ni) electrode in KOH-H 2 O system at 160 °C, focusing on the electrode’s morphology and performance changes under cathodic polarization. At a current density of 10 mA cm –2 , electrolysis voltage decreases with increasing temperature and electrolyte concentration, from 2.03 V in 1 M KOH at 25 °C to 1.81 V in 30 wt% KOH at 80 °C, and further to 1.59 V in 85 wt% KOH at 160 °C, respectively. In parallel, the corrosion rate increases from 0.008 mm y –1 to 0.023 mm y –1 , and reaches a peak of 0.096 mm y –1 under a current density of 200 mA cm –2 , respectively. The onset potential for cathodic corrosion shifts positively from –1.8 V vs Pt in 30 wt% KOH at 80 °C to –1.7 V in 85 wt% KOH at 160 °C. Preferential corrosion occurs at the surface imperfections, such as defects, scratches, and cavities. Cathodic corrosion results in the refinement of surface grains on the Ni electrode, increasing the electrochemical active surface area. However, this process concurrently reduces the efficacy of the catalyst for hydrogen evolution due to the preferential exposure of the low-energy Ni(111) crystalline facets.