Ni–Mo–O alloy cathodes for hydrogen evolution in hot concentrated NaOH solution

Nickel–molybdenum–oxygen alloy cathodes prepared by arc ion plating technique are found to have excellent catalytic activity and durability in the electrolysis of 32.5 wt.% NaOH at 90°C. The catalytic activity is strongly affected by the molybdenum and oxygen content in the alloys. The optimized compositions are between 10 and 20 at.% molybdenum and 5 and 10 at.% oxygen, giving a hydrogen overpotential of less than 100 mV at 4×103 A m−2. Furthermore, the cathodes exhibit excellent stability compared with the currently used nickel–sulphur cathode. The decrease in the overpotential by the oxygen addition is attributed to the increase in effective surface area and the enhancement of the rate determining electrochemical desorption of adsorbed hydrogen.