| Summary: | Mg-based materials with added C60 and/or Fe, i.e., Mg-C60, Mg-Fe and Mg-C60-Fe, were prepared by ball milling. We also added stearic acid (SA) as a process control agent to Mg-Fe + SA and Mg-C60-Fe + SA. We investigated the effects of C60, Fe and stearic acid on the hydrogen storage properties of Mg by X-ray diffraction (XRD), morphology observation, differential scanning calorimetry and pressure-composition-temperature measurements using Sievert apparatus under lower hydrogen pressure (<1.0 MPa). Morphology observation revealed that the particles of Mg-Fe + SA, Mg-C60-Fe and Mg-C60-Fe + SA were less agglomerated than Mg-Fe, and also nanoparticles of C60 were formed on the surface of the C60-added samples. We observed MgO in the as-milled samples of Mg-Fe + SA and Mg-C60-Fe + SA, and MgH2 in all the Fe-added samples after hydrogenation at 280℃ under a hydrogen pressure of 0.99 MPa with XRD analysis. The Fe-added samples released hydrogen at temperatures 71-152℃ lower than commercial MgH2 in DSC analysis. The hydrogen storage capacities of Mg-Fe + SA and Mg-C60-Fe + SA were 2.93 wt.% and 2.42 wt.%, respectively, and they did not release hydrogen at 280℃ even the equilibrium pressure as below 0.1 MPa. On the other hand, Mg-Fe and Mg-C60-Fe absorbed hydrogen up to 2.57 wt.% and 3.10 wt.%, respectively, and released hydrogen at 280℃ and about 0.1 MPa. The Fe had a catalytic effect on Mg, and stearic acid oxidized Mg during ball milling, although it refined the particles. In contrast, C60 inhibited agglomeration without oxidizing Mg and dispersed Fe finely on it, and also increased specific surface area by the nanoparticles provided the more active sites for hydrogenation. The co-addition of C60 and Fe exhibit the synergetic effects in enhancing the hydrogen storage properties of Mg.
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