Anodic and cathodic process of hypophosphite on a Ni-Ag electrode

The reduction and the oxidation of hypophosphite on a Ni-Ag electrode have been studied to provide the information about the phosphorus incorporation mechanisms during the electroless deposition and the electrodeposition of Ni-P alloys. In the electrooxidation process, an absorbency band around 240 nn, which was ascribed to the formation of an intermediate (PHO2-)-P-., was observed by in situ UV-Vis subtractive reflectance spectroscopy. Accordingly, the electrooxidation of hypophosphite might undergo an H abstraction of hypophosphite from the PH bond to form the phosphorus-centred radical (PHO2-)-P-., which was subsequently electrooxidized to the final product, phosphite. In the reduction process Ni-phosphine compound Ni-(PH3)(n) was observed by irt situ surface Raman spectroscopy. The results from the Raman experiments show that, in the NiSO4-free solution, hypophosphite was reduced only to Ni-phosphine compound, while in the case where NiSO4 coexisted in the solutions, the Ni-phosphine compound, as an intermediate, was oxidised by Ni2+ to elemental phosphorus in alloys with nickel acting as the catalyst