ROLE OF ELECTROMC, GEOMETRIC, AND SURFACE PROPERTIES ON THE MECHANISM OF THE ELECTROCHEMICAL HYDRIDING/DEHYDRIDING REACTIONS

摘要

Since 1990, there has been an ongoing collaboration among the authors to investigate the role of individual elements on the thermodynamics and kinetics of hydriding/dehydriding reactions of some AB_5 alloys from the gas phase and as hydride electrodes. This review article presents the electrochemical and physicochemical characteristics of hydriding/dehydriding reactions in respect to their dependence on electronic, geometric and surface properties of the hydride materials. Electrochemical Impedance Spectroscopy (EIS), X-ray absorption spectroscopy (XAS), X-ray diffraction spectroscopy (XRD), and scanning vibrating electrode technique (SVET) studies were carried on AB_5 type alloys, partially substituted by other elements. Expansion of the unit cell volume and a larger Ni d band vacancy are beneficial for increasing the amount of hydrogen storage. XAS and SVET showed that the Ce substitution for La in the AB_5 alloy enhances the lifetime of the hydride electrode.