The effect of palladium coating on hydrogen storage alloy electrodes for nickel/metal hydride batteries

Abstract

Este trabalho apresenta estudos de carga/descarga realizados sobre ligas metálicas multi componentes ("misch metal al loys") recobertas com Paládio e que podem ser utilizadas como eletrodos em baterias de níquel/hidreto metálico. Foi determinado o efeito do recobrimento nas características voltamétricas, no ciclos de vida e na capacidade sob diversos re gimes de descarga para os eletrodos de liga metálica. O número de ciclos necessários para ativar os eletrodos de liga metálica diminui quando o conteúdo de Pd aumenta. Os resultados mostram também que as ligas recobertas com Pd apresentam uma maior capacidade de carga e um desempenho melhor que aquelas sem o Pd. Essas melhores características podem ser atribuídas ao efeito catalítico do Pd sobre a reação de hidr ogênio. .Charge / dis charge stud ies car ried out on Pd -coated misch metal -based al loys for use in nickel-metal hy dride bat ter ies are pre sented. The ef fect of Pd coat ing on the voltammetric ch arac ter is tics, life cy cle be hav ior, and rate ca pa bil ity of the al loy elec trodes was de ter mined. The num ber of cy cles re quired to ac ti vate the al loy elec trodes de creases with an in crease in t he Pd con tent. The re sults also show that Pd -coated al loys ex hibit higher stor age ca pac i ties an d better per for mance than bare al loys.This im proved per for mance can be at trib uted to the cat alytic ef fect of Pd on the hy dro gen elec trode re ac tion. Key words: metal hy dride elec trodes, hy dro gen stor age ca pac ity, pal la dium coat ing In tro duc tionAt pres ent there is a re newed in ter est in re search on hy drogen re vers ible stor age re sult ing from the rec og ni tion of the many po ten tial ad van tages of such a sys tem for use in elec trochem i cal en ergy stor age de vices. For ex am ple, in power sources that uti lize hy dro gen as a fuel, the chem i cal stor age of hy dro gen as a metal hy dride may lead to a con sid er able re duction in op er at ing pres sures and vol ume. Vol u met ric en ergy den si ties com pa ra ble to those of cryo genic hy dro gen can be at tained for ap pli ca tions where the weight is less im por tant, such as in the ter res trial stor age of so lar-electrolytic hy dro gen, and when the bi-functional hy dro gen elec trode is em ployed in al ka line bat ter ies. When fully de vel oped, Ni-MH bat ter ies, for ex am ple, will ad e quately re place the ex ist ing Ni-Cd bat teries for sev eral sta tion ary (re serve and emer gency power sources, emer gency light ing in pub lic build ings such as schools, hos pi tals, etc.) and por ta ble (video cam eras, cel lu lar tele phones, lap-top com put ers, etc.) ap pli ca tions. The ad vantages of Ni-MH bat ter ies over the Ni-Cd sys tem are: (i) a higher cell en ergy den sity, and (ii) the elim i na tion of toxic cad mium thereby pre vent ing en vi ron men tal dam age. Fur thermore, the de vel op ment of Ni-MH bat ter ies will make them poten tial can di dates for trans por ta tion ap pli ca tions, such as in elec tric ve hi cles, with large ben e ...

Effect of additional catalytic phases imposed by sintering on the hydrogen absorption behavior of AB2 type Zr-based alloys

“…13). Hence, the overpotential decrease and the electrochemical reversibility of the alloys increase [8]. This behavior is clearly enhanced in the secondary phases-bearing alloys.…”

Analysis of pressure variations in a low-pressure nickel–hydrogen battery. Part 2: Cells with metal hydride storage

“…The smaller particles produced by pulverization are still active for the hydrogen absorption/desorption reaction which occurs through the interaction of hydrogen gas with the hydrogen storage material. Researchers have also shown that the addition of palladium enhances the kinetics of the hydrogen absorption/desorption reactions due to the electrocatalytic effect of palladium [20, 21, 25–27]. …”

Electrochemical and X-ray absorption spectroscopy studies of copper coatings on a hydrogen storage alloy

“…One of the problems associated with the use of metal hydride electrodes is the performance degradation upon cycling, which is associated with the oxidation of the alloy elements. Thus, the microencapsulation with several metals has been studied as a way of protecting the alloy powder particles against corrosion [1][2][3][4][5][6][7][8].…”