In situ Raman studies on cathodically deposited nickel hydroxide films and electroless Ni-P electrodes in 1 M KOH solution

Three types of working electrodes, as-deposited nickel hydroxide. deactivated nickel hydroxide, and electroless Ni-P electrode, are studied in this work. The surface state of the electrodes varying with potential are investigated using cyclic voltammetry techniques combined with in situ Raman spectroscopy in 1 M KOH solution. As-deposited nickel hydroxide is electrooxidized to the oxides of higher state with Raman characteristic bands, 475 and 55 cm(-1), and the corresponding reaction is assigned to be a alpha-Ni-(OH)(2)/gamma-NiOOH redox reaction in the potential range between 350 and 500 mV. When the film is deactivated by voltammetric cycling, the phases, beta-Ni(OH)(2), and some untransformed alpha-Ni(OH)(2) are present. beta-Ni(OH)(2) will he electrooxidized to beta-NiOOH, which has Raman characteristic bands of 480 and 560 cm(-1) in the anodic sweep between 350 and 450 mV. The redox pair on the electroless Ni-P electrode is recognized as beta-Ni(OH)(2)/beta-NiOOH because of the identical Raman bands with beta-NiOOH, namely, 480 and 560 cm(-1) after being electrooxidized.