Faradic responses of nickel electrode were detected in rather negative potential region by AC voltammetry in basic solution. Based on the incipient hydrous oxide adatom mediator model, the oxidation of nickel atoms at the defects to nickel hydrous oxide lead to the Faradic responses. Hypophosphite oxidation and the formation of nickel hydrous oxide began at the same potential, so nickel hydrous oxide may play the role of catalyst for hypophosphite oxidation.