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 -1.0V (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 a-nickel hydroxide, were observed, nickel is oxidized to a-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.