Superior electrochemical hydrogen storage properties of binary Mg–Y thin films

•Pd-capped binary Mg–Y thin films were prepared by magnetron co-sputtering.•Mg–Y films are intermetallic with ultrafine nanocrystalline structure.•Mg–Y films show superior electrochemical hydrogen storage properties.•Mg78Y22 film achieves a high discharge capacity about 1590 mAh g−1.

Mg–Y thin films capped with Pd have been prepared by direct current magnetron co-sputtering system. It is found that Mg alloyed with Y in film state forms ultrafine nanocrystalline intermetallic compounds. The structure together with the catalytic effect of Y gives rise to a high electrochemical hydrogen storage capacities and superior activation properties. It is worthy to note that Mg78Y22 film achieves a high discharge capacity of 1590 mAh g−1 without requiring activation process. Moreover, Mg alloyed with Y effectively improves the cyclic stability of Mg-based films ascribing to the anti-corrosion role of Y. For Mg37Y63 film, more than 92％ of the maximum discharge capacity can be maintained after 100 charge–discharge cycles.