Composites for hydrogen storage by mechanical grinding of graphite carbon and magnesium

摘要

Novel hydrogen storage Mg/G nano-composites obtained by mechanical grinding of magnesium (Mg) and graphite carbon (G) with organic additives (benzene, cyclohexane or tetrahydrofuran) have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) and temperature programmed desorption (TPD) techniques. The occurrence of various effects as a result of the formation of Mg/G composites ground with benzene, cyclohexane or tetrahydrofuran (designated hereafter as (Mg/G))_(BN), (Mg/G)_(CH) or (Mg/G)_(THF), respectively is expected. Upon mechanical grinding with benzene or cyclohexane for 4-40 h, new hydrogen-storing sites, other than those due to the magnesium component, were formed in the Mg/G composites and they took up hydrogen reversibly. The cleavage-degraded graphite in the composites plays an important role in such hydrogen uptake and release. The formation of Mg/G composites upon grinding with the organic additives led to not only a drop in the onset temperature of MgH_2 decomposition, but the formation of additional hydrogen uptake site. In marked contrast to (Mg/G)_(BN) and (Mg/G)_(CH), the composites ground without any additives (referred as (Mg/G)_(none)) did not show such behavior. The effective nano-composites are those in which there are synergetic interaction between magnesium and graphite as a result of mechanical grinding with the organic additives.