Effect of Zn additives to the electrolyte on the corrosion and cycle life of some AB(5)H(x) metal hydride electrodes

Investigation on a series of AB(5)-type metal hydride electrodes reveals significant improvement of cycle life in the presence of zincate electrolytes (0.5 M ZnO in 6 M KOH) for alloys without substituents such as Ce. For alloys containing Ce, which are known to impart passive protection against corrosion no additional advantage was derived by using zincate electrolytes. X-ray absorption near-edge structure investigation at the Ni K edge, due to its relative high abundance and catalytic importance in the hydriding process, was used to elicit the corrosion characteristics as a function of cycling. The spectra averaged over the bulk of the sample (transmission mode) and those from the top 200 to 250 Angstrom (electron yield mode) indicate significant lowering of corrosion and buildup of NI(OH)(2) in non-Ce substituted alloys when using zincate electrolytes. In Ce substituted samples this effect was marginal.