Influence of multiple oxide (Cr2O3/Nb2O5) addition on the sorption kinetics of MgH2

The influence of multiple additions of two oxides, Cr2O3 and Nb2O5, as additives on the hydrogen sorption kinetics of MgH2 after milling was investigated. We found that the desorption kinetics of MgH2 were improved more by multiple oxide addition than by single addition. Even for the milled MgH2 micrometric size powders, the high hydrogen capacity with fast kinetics were achieved for the powders after addition of 0.2 mol% Cr2O3 + 1 mol% Nb2O5. For this composition, the hydride desorbed about 5 wt.% hydrogen within 20 min and absorbed about 6 wt.% in 5 min at 300 degrees C. Furthermore, the desorption temperature was decreased by 100 degrees C, compared to MgH2 without any oxide addition, and the activation energy for the hydrogen desorption was estimated to be about 185 kJ mol(-1), while that for MgH2 without oxide was about 206 kJ mol(-1). (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.