Mechanically milled coal and magnesium composites for hydrogen storage

Anthracite-magnesium composites were prepared via reactive ball milling in cyclohexene, leading to up to ∼0.6% hydrogen evolution at atmospheric pressure and temperatures up to 1273 K. Hydrogen evolution, measured with temperature programmed desorption coupled with mass spectroscopy (TPD-MS), is attributed to dehydrogenation of cyclohexene within the mill. The similarity of the TPD-MS to other reports for carbon-based samples is discussed. No metal hydrides were detected in XRD of the as-milled materials. The hydrogen evolution occurred at lower temperatures (up to 150 K less) than that expected for magnesium or added metals. The intensity and temperature of only one TPD-MS peak (occurring at 780-840 K) was dependent upon Mg addition. Subsequent hydrogen uptake studies after extended degassing of the milled material suggested the hydrogen uptake was reversible and the structures were not fully saturated by milling, with a rapid uptake of 0.3-0.54% at room temperature and atmospheric pressure.