The intermetallic compound Mg0.65SC0.35 was found to form a nano-structured metal hydride composite system after a (de)hydrogenation cycle at temperatures up to 350 degrees C. Upon dehydrogenation phase separation occurred forming Mg-rich and Sc-rich hydride phases that were clearly observed by SEM and TEM with the Sc-rich hydride phase distributed within Mg/MgH2-rich phase as nano-clusters ranging in size from 40 to 100 nm. The intermetallic compound Mg0.65SC0.35 showed good hydrogen uptake, ca. 6.4 wt.%, in the first charging cycle at 150 degrees C and in the following (de)hydrogenation cycles, a reversible hydrogen capacity (up to 4.3 wt.%) was achieved. Compared to the as-received MgH2, the composite had faster cycling kinetics with a significant reduction in activation energy Ea from 159 +/- 1 kJ mol(-1) to 82 +/- 1 kJ mol(-1) (as determined from a Kissinger plot). Two-dehydrogenation events were observed by DSC and pressure-composition-isotherm (PCI) measurements, with the main dehydrogenation event being attributed to the Mg-rich hydride phase. Furthermore, after the initial two cycles the hydrogen storage capacity remained unchanged over the next 55 (de)hydrogenation cycles. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.