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 electro-less deposition and the electrodeposition of Ni-P alloys.In the electrooxidation process,an absorbency band around 240nm,which was ascribed to the formation of an intermediate PHO2-,was observed by in situ UV-Vis subtractive reflectance spectroscopy.Accordingly,the electrooxidation of hypophosphite might undergo an H abstraction of hypophosphite from the P-H bond to form the phosphorus-centred radical ’ PHO2- ,which was subsequently electrooxidized to the final product,phosphite.In the reduction process Ni-phos-phine compound Ni-(PH3)n was observed by in 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 oxidise The reduction and the oxidation of hypophosphite on a Ni-Ag electrode have been studied to provide the information about the phosphorus incorporation mechanisms mechanisms of the electro-less deposition and the electrodeposition of Ni-P alloys. In the electrooxidation process, an absorbency band around 240 nm , which was ascribed to the formation of an intermediate PHO2-, was observed by in situ UV-Vis subtractive reflectance spectroscopy. Accreditedly, the electrooxidation of hypophosphite might undergo an H abstraction of hypophosphite from the PH bond to form the phosphorus-centred radical ’ PHO2-, which was subsequently electrooxidized to the final product, phosphite. The reduction process Ni-phos-phine compound Ni- (PH3) n was observed by in 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 interm ediate, was oxidise