Hydrogen storage properties of magnesium hydride catalyzed byNi-based solid solutions
(1. Hunan Provincial Key Laboratory of Intelligent Manufacturing Technology for High-performance Mechanical Equipment, Changsha University of Science and Technology, Changsha 410114, China;
2. Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation,Changsha University of Science and Technology, Changsha 410114, China;
3. College of Materials Science and Engineering, Hunan University, Changsha 410082, China)
2. Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation,Changsha University of Science and Technology, Changsha 410114, China;
3. College of Materials Science and Engineering, Hunan University, Changsha 410082, China)
Abstract: The Ni-25%X (X=Fe, Co, Cu, molar fraction) solid solutions were prepared and then doped into MgH2 through high-energy ball milling. The initial dehydrogenation temperatures of MgH2/Ni-25%X composites are all decreased by about 90 °C relative to the as-milled pristine MgH2. The Ni-25%Co solid solution exhibits the most excellent catalytic effect, and the milled MgH2/Ni-25%Co composite can release 5.19 wt.% hydrogen within 10 min at 300 °C, while the as-milled pristine MgH2 can only release 1.78 wt.% hydrogen.More importantly, the dehydrogenated MgH2/Ni-25%Co composite can absorb 5.39 wt.% hydrogen at 275 °C within 3 min. The superior hydrogen sorption kinetics of MgH2/Ni-25%Co can be ascribed to the actual catalytic effect of in-situ formed Mg2Ni(Co) compounds. First-principles calculations show that the hydrogen absorption/desorption energy barriers of Mg/MgH2 systems decrease significantly after doping with transition metal atoms, which interprets well the improved hydrogen sorption properties of MgH2 catalyzed by Ni-based solid solutions.
Key words: MgH2; Ni-based solid solutions; catalytic effect; hydrogen storage properties; first-principles calculations