Influence of tin on the electrochemical and gas phase hydrogen sorption in Mg2−xSnxNi (x = 0, 0.1, 0.3)

Mg2−xSnxNi (x = 0, 0.1, 0.3) alloys were synthesized by reactive ball milling under protective Ar atmosphere and liquid n-heptane. The microstructure and the morphology of the powders were determined by X-ray diffraction and scanning electron microscopy. The as-milled alloys consist of Mg2Ni nanocrystals with an average grain size in the range 3–7 nm, depending on the alloy composition. Sn containing phases were not detected even in the Sn-rich alloy. Obviously, Sn is dissolved in the Mg2Ni intermetallic compound. Gas phase sorption of hydrogen was not observed in the alloys containing Sn (Mg2−xSnxNi; x = 0.1, 0.3). It was suggested that Sn impedes the process of hydrogen molecules decomposition. The as-milled alloys absorbed reversibly hydrogen electrochemically. Mg2Ni alloy showed the highest discharge capacity of 300 mAh/g. The capacity of Mg1.9Sn0.1Ni and Mg1.7Sn0.3Ni was about 260 mAh/g. It was found that Sn improved the cycle life of the electrode.