Hydrogen storage properties of a Mg-Ni-Fe mixture prepared via planetary ball milling in a H_2 atmosphere

摘要

A sample composition has been designed based on previously reported data. An 80 wt% Mg-13.33 wt%Ni-6.67 wt%Fe (referred to as Mg-13.33Ni-6.67Fe) sample exhibited higher hydriding and dehydriding rates after activation and a larger hydrogen storage capacity compared to those of other mixtures prepared under similar conditions. After activation (at n = 3), the sample absorbed 4.60 wt%H for 5 min and 5.61 wt%H for 60 min at 593 K under 12 bar H_2. The sample desorbed 1.57 wt%H for 5 min and 3.92 wt%H for 30 min at 593 K under 1.0 bar H_2. Rietveld analysis of the XRD pattern using FullProf program showed that the as-milled Mg-13.33Ni-6.67Fe sample contained Mg(OH)_2 and MgH_2 in addition to Mg, Ni, and Fe. The Mg(OH)_2 phase is believed to be formed through the reaction of Mg or MgH_2 with water vapor in the air. The dehydrided Mg-13.33Ni-6.67Fe sample after hydriding-dehydriding cycling contained Mg, Mg_2Ni, MgO, and Fe.