Effect of nanostructure and partial substitution on gas absorption and electrochemical properties in Mg2Ni-based alloys

Mg2Ni-based alloys have been intensively investigated as gaseous hydrogen absorption materials and negative electrode materials for Nickel-Metal Hydride (Ni-MH) battery. In this work, three Mg2Ni-based samples (micrometer Mg2Ni, nanometer Mg2Ni and nanometer Mg2Ni0.75Cu0.25) were synthesized from Mg, Ni and Cu nanoparticles and commercially available micrometer Ni particles. The metal nanoparticles were fabricated by hydrogen plasma metal reaction technique. The structure and morphology of these three Mg2Ni-based samples were studied. Gaseous hydrogen absorption and electrochemical properties of these samples were investigated and compared. Amongst these three samples, the nanometer Mg2Ni shows best gas absorption kinetics of 3.0 wt.% in 1 min under 4 MPa hydrogen at 623 K; the nanometer Mg2Ni0.75Cu0.25 sample shows a highest first cycle electrochemical capacity of 346 mAh/g. The effect of nanostructure and partial substitution on gas absorption and electrochemical performance was clarified.