The Deactivation of Nickel Hydroxide to Hypophosphite Electrooxidation on a Nickel Electrode

The deactivation of nickel hydroxide to the electrooxidation of hypophosphite on a nickel electrode was studied by means of in situ UV-Vis subtractive reflectance spectroscopy. The experimental results show that when the potential is lower than -1.0 V (SCE), the surface on nickel electrode is free of nickel hydroxide, on which hypophosphite is active. When the potential moves positively to about 0.75V, two absorbency bands around 300nm and 550nm, which were ascribed to the formation of α-nickel hydroxide, were observed, nickel is oxidized to α-nickel hydroxide. Severe deactivation of the surface occurs when the nickel surface is covered with nickel hydroxide, which separates the hypophosphite ion from nickel substrate.