The Investigation On The Hydrogen Storage Performance Of The As-cast And As-milled La_2-xCe_xMg₁₆Ni（x=0,0.1,0.2,0.3,0.4）

Magnesium is rich, lightweight, high hydrogen storage capacity, high electrochemicalcapacity, low cost and low environmental impact, so magnesium based alloys areconsidered as very promising hydrogen storage materials and have gained a widespreadconcern. La2Mg17storage alloy has high hydrogen storage capacity among the magnesiumbased materials. Unfortunately, the practical application of the La2Mg17alloy is seriouslyfrustrated by high thermodynamic stability and sluggish kinetics of its hydride. Ni hasgood catalytic activity. The as-cast La2-xCexMg16Ni (x=0,0.1,0.2,0.3,0.4) hydrogenstorage alloys are prepared by induction melting method through Ni partially substitute Mgand Ce partially substitute La of the La2Mg17. The as-cast alloy is mixed with100%and200%Ni power for ball milling to obtain balling milled hydrogen storage alloy. The as-castand balling milled hydrogen storage alloy are researched though hydrogen absorption anddesorption kinetics of different temperature, electrochemical and electrochemical dynamics.The change of structure of hydrogen storage alloys is detected by XRD and TEM. Thedifference of the performance of as-cast and balling milled hydrogen storage alloys and thechange of quantity of partial substitution are analyzed.As-cast hydrogen storage alloy need seven times absorption and desorption hydrogencycles for fully activated, the time nearly are twenty four hours. It is fully activated at firsttime when mixed with100%Ni for ball milling. The time is about one hour. It is also fullyactivated at first time when mixed with200%Ni for ball milling, and the rate of absorptionand desorption hydrogen is more fast than mixed with100%Ni. The rate of absorption anddesorption hydrogen of experimental samples are increasing with amounts of ceriumsubstitution. The activation energy of absorption and desorption hydrogen of alloys reducewith increasing amounts of Ce substitution, which are calculated though the absorption anddesorption hydrogen curves of three temperatures. The maximum electrochemical capacityof ball milled alloy with200%Ni for20h are922.6mAh/g,922.2mAh/g,914.1mAh/g,872.5mAh/g and782.5mAh/g. Obviously, the electrochemical capacity is reduce with increasing amounts of Ce substitution. The HRD is same as the electrochemical capacity.The electrochemical impedance spectra (EIS) and activation enthalpy increase with theamounts of cerium substitution increased. The Tafel polarization curves and potential-stepcurves increase with the cerium substitution.The phases of alloy and lattice distortion are increased with amounts of ceriumsubstitution increased. The cerium substitution increased can make absorption anddesorption hydrogen ability of alloys increase. Nanocrystal/amorphous can be made bymechanical alloying. Increasing the balling time can increase the amorphous content ofalloys. But too much amorphous will block absorption of hydrogen atom and result in thedecrease of hydrogen absorption capacity and hydrogen absorption rate. The increase of Nipower could promote the increase of amorphous phase. On the other hand, the addition ofNi power can enhance the rate of hydrogen absorption and absorption capacity and theelectrochemical discharge capacity. But the radius of cerium is smaller than La, it isunfavorable for absorption of hydrogen atom, so the rate of hydrogen absorption，absorption capacity and activation enthalpy are reduced.