Investigation of modification of hydrogenation and structure properties of multi-substituted LaNi5 alloys

Multi-substituted LaNi5 alloys prepared by annealing, activating, and cycling were investigated systematically using synchrotron radiation X-ray diffraction (XRD), extended X-ray absorption fine structure spectroscopy (EXAFS), and X-ray photoelectron spectroscopy to clarify the evolution of the structural properties of the alloys. XRD and Rietveld analysis results show that annealing and activation can cause changes in the isotropy of the lattice constants of the LaMnxNiy phase. EXAFS data on the La-L3-edge show variations in atomic distances between La–Mn and La–Ni during annealing. Chemical shifts in the La 3d and Ni 2p core levels induced by activation can be determined with very high levels of accuracy using energy differences ΔEB (Ni 2p1/2–La 2d5/2). The decrease in the cycling capacity may also be attributed to the oxidation of La and Ni in the alloys during cycling, which can resist the reaction of hydrogen absorption.