Enhancement of hydrogen uptake for Y and Gd films by thin Ni surface overlayers

To reduce the hydrogen pressure and onset temperature for formation of the trihydrides of Y and Gd, we used Ni as a catalytic layer. The Y and Gd films capped with the Ni layer, which were grown by electron beam evaporation method, were hydrogenated in H2 pressure less than ∼3×103Pa, which is fairly lower than conventional pressures (∼1×106Pa) used for hydrogen absorption in Y and Gd. The reaction temperature was varied from 20 to 200 °C. Also, we prepared Pd capped films, and compared their hydrogenation results with those on Ni capped case. For Ni capped films, the formation of YH3 and GdH3 is observed at 68 and 89 °C, respectively. For Pd capped case, on the other hand, the formation of YH3 is observed at 300 °C. The presence of Ni capping layer, instead of Pd, greatly enhances hydrogen absorption in Y and Gd so that we can substantially reduce the hydrogen pressure and onset temperature for the formation of trihydrides of Y and Gd.

► Ni capped Y and Gd films were grown by electron beam evaporation.
► Ni capped films were hydrogenated at low temperature and in low hydrogen temperature.
► Structural characterization was carried out X-ray diffraction.
► Ni capped films show superior hydrogen activity.