MgH2 dehydrogenation properties improved by MnFe2O4 nanoparticles

The catalytic effects of MnFe2O4 nanoparticles on the dehydrogenation properties of MgH2, prepared by ball milling, are investigated for the first time. The onset dehydrogenation temperature for MgH2 + 7 mol % MnFe2O4 is 300 degrees C, 140 degrees C lower, compared with the as-received MgH2. The isothermal dehydriding kinetics shows that 7 mol% MnFe2O4-doped sample can release 5.05 wt.% hydrogen in 1 h at 300 degrees C under 0.1 MPa pressure, whereas as-received MgH2 releases only 0.49 wt.% hydrogen for the same conditions, indicating significantly improved dehydrogenation. From the differential scanning calorimetry and the Kissinger desorption kinetics analysis, the apparent activation energy of 7 mol% MnFe2O4-doped sample is 64.55 kJ mol(-1), resulting in 190.34 kJ mol(-1) decrease, compared with the as-received MgH2, which is lower than that of MgH2 doped with other reported transition metal oxide catalysts. Based on X-ray diffraction and X-ray photoelectron spectroscopy tests, Mg2MnO4 and Fe0.872O phases together play a synergistic role in remarkably improving MgH2 dehydriding properties. (C) 2013 Elsevier B.V. All rights reserved.