Amorphous LaNi thin film electrodes

Amorphous LaNi thin films over a wide range of composition were fabricated by electron beam evaporation in ultra-high vacuum. The structure and composition of these films were determined by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA). The reversible hydrogen storage capacity was determined by electrochemical cycling. The equilibrium electrochemical potential of these thin-film electrodes was also measured versus the change of hydrogen concentration, ΔH/M, in these films. The smallest value among the maximum ΔH/M of these amorphous films is about 0.38, which is still much larger than the one reported in the literature (∼0.1). Harris's model for hydrogen absorption in amorphous transition metal alloys is applied to the amorphous LaNi system. We found that both the LaNi₃ and the La₂Ni₂ type of tetrahedral sites can store hydrogen.