ELECTROOXIDATION OF HYPOPHOSPHITE IONS ON NICKEL SINGLE-CRYSTAL ELECTRODES

The electrocatalytic oxidation of hypophosphite ion on Ni (100), Ni (111) and Ni (210), in an alkaline medium, has been studied by cyclic voltammetry and chronoamperometry. Two surfaces preparation methods have been employed (electrochemical polishing followed, or not, by uhv-treatment) and the well defined uhv prepared surfaces characterized by LEED and AES. The corresponding cyclic voltammograms have shown that the (210) face displays the highest catalytic activity. In the case of the (111) and (100) planes, chronoamperometric and voltammetric data have revealed that the tendency to oxidize the hypophosphite ion is determined by the effect of the crystal structure on the anodic oxidation of nickel, as well as on the hydrogen evolution reaction. Nevertheless, the (111) face appears to be the most sensitive to the inhibition of hypophosphite oxidation, in which the beta-Ni(OH)(2) formation is partially responsible.