Raman spectroscopic study on the surface oxide layer of AB 5-type metal hydride electrodes

Abstract

In conjunction with electrochemical techniques, the microscopic properties and Raman spectra of AB 5-type metal hydride (MH) electrodes at different potentials or after different charge–discharge cycles were characterized by the confocal microprobe Raman method. The experimental results indicate that a composite oxide layer was produced and different Raman spectra were observed for MH electrode at different charge–discharge stages. It is proposed that nickel plays a main role in the composite surface oxide layer as reactive sites for electrochemical reaction while other components are dispersed evenly to provide a stable corrosion resistance layer to the corrosive electrolyte. Moreover, it was demonstrated that Co, Mn and other alloy components due to their affinity with water, segregated and were enriched progressively in the alloy surface layer, where they subsequently produced oxides, which should be an important cause for the deterioration of MH electrodes.