Structure and Electrochemical Hydrogen Storage Properties of as-Milled Mg–Ce–Ni–Al-Based Alloys

Abstract

At room temperature, crystalline Mg-based alloys, including Mg2Ni, MgNi, REMg12 and La2Mg17, have been proved with weak electrochemical hydrogen storage performances. For improving their electrochemical property, the Mg is partially substituted by Ce in Mg–Ni-based alloys and the surface modification treatment is performed by mechanical coating Ni. Mechanical milling is utilized to synthesize the amorphous and nanocrystalline Mg1−xCexNi0.9Al0.1 (x = 0, 0.02, 0.04, 0.06, 0.08) + 50 wt%Ni hydrogen storage alloys. The effects made by Ce substitution and mechanical milling on the electrochemical hydrogen storage property and structure have been analyzed. It shows that the as-milled alloys electrochemically absorb and desorb hydrogen well at room temperature. The as-milled alloys, without any activation, can reach their maximal discharge capacities during first cycling. The maximal value of the 30-h-milled alloy depending on Ce content is 578.4 mAh/g, while that of the x = 0.08 alloy always grows when prolonging milling duration. The maximal discharge capacity augments from 337.4 to 521.2 mAh/g when milling duration grows from 5 to 30 h. The cycle stability grows with increasing Ce content and milling duration. Concretely, the S100 value augments from 55 to 82% for the alloy milled for 30 h with Ce content rising from 0 to 0.08 and from 66 to 82% when milling the x = 0.08 alloy mechanically from 5 to 30 h. The alloys’ electrochemical dynamics parameters were measured as well which have maximum values depending on Ce content and keep growing up with milling duration extending.