Progress in the understanding of the hypophosphite oxidation on nickel single crystals

Abstract

The relative electroactivities of different nickel surface structures, polycrystalline and (100), (111) and (210) planes, towards the hypophosphite ion oxidation are evaluated under carefully selected conditions to avoid both the electrode surface oxidation and background electrolyte competitive adsorption. Voltammetric and chronoamperometric studies have shown the hypophosphite ion oxidation dependence on time, potential and electroactive species concentration. The time dependent step involves radical intermediate formation responsible for the autocatalytic oxidation. The potentials where the oxidation onset is observed indicates that the most catalytic surface is the Ni(210). In the present medium, at a pH of 6, the relative ability of the (111) and (100) planes deviates from that observed in alkaline media where the β-Ni(OH) 2 formation contributes for the lowest catalytic activity exhibited by the Ni(111).