Abstract
Abstract The influence of multiple additions of two oxides, Cr 2 O 3 and Nb 2 O 5 , as additives on the hydrogen sorption kinetics of MgH 2 after milling was investigated. We found that the desorption kinetics of MgH 2 were improved more by multiple oxide addition than by single addition. Even for the milled MgH 2 micrometric size powders, the high hydrogen capacity with fast kinetics were achieved for the powders after addition of 0.2 mol% Cr 2 O 3 + 1 mol% Nb 2 O 5 . For this composition, the hydride desorbed about 5 wt.% hydrogen within 20 min and absorbed about 6 wt.% in 5 min at 300 °C. Furthermore, the desorption temperature was decreased by 100 °C, compared to MgH 2 without any oxide addition, and the activation energy for the hydrogen desorption was estimated to be about 185 kJ mol −1 , while that for MgH 2 without oxide was about 206 kJ mol −1 .
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