Sorption and desorption properties of a CaH2/MgB2/CaF2 reactive hydride composite as potential hydrogen storage material

The hydrogenation behavior of 3CaH2+4MgB2+CaF2 composite was studied by manometric measurements, powder X-ray diffraction, differential scanning calorimetry and attenuated total reflection infrared spectroscopy. The maximum observed quantity of hydrogen loaded in the composite was 7.0 wt%. X-ray diffraction showed the formation of Ca(BH4)2 and MgH2 after hydrogenation. The activation energy for the dehydrogenation reaction was evaluated by DSC measurements and turns out to be 162±15 kJ mol−1 H2. This value decreases due to cycling to 116±5 kJ mol−1 H2 for the third dehydrogenation step. A decrease of ca. 25–50 °C in dehydrogenation temperature was observed with cycling. Due to its high capacity and reversibility, this composite is a promising candidate as a potential hydrogen storage material.

PCI of 3CaH2+4MgB2+CaF2 reactive hydride composite at 325 °C and 350 °C. Open marks: dehydrogenation, closed marks: hydrogenation.Figure optionsDownload as PowerPoint slideHighlights
► The hydrogenation and dehydrogenation behavior of CaF2 doped CaH2/MgB2 RHC is presented.
► The new composite presents a superior hydrogen uptake compared with the non-doped composite..
► A reduction in the Ea and the dehydrogenation temperature was observed by CaF2 doping and cycling.