Effect of BaO on Hydrogen Sorption Performance of Mg17Al12: Experimental and Theoretical Studies.

The Mg17Al12-BaO composite is synthesized via mechanical milling and the effect of BaO on the hydrogen sorption properties of Mg17Al12 is studied. Experimentally, we prepare the Mg17Al12-Ba, Mg17Al12-BaO, Mg17Al12-BaF2, and Mg17Al12-BaCl2 mixtures and find that the Mg17Al12-BaO composite shows a superior hydrogen storage performance. For instance, the hydrogenation (dehydrogenation) enthalpy of the Mg17Al12 decreases from 62.4 (91.2) to 58.6 (71.7) kJ mol-1 after adding BaO. When 1.0 wt % of H2 is absorbed/desorbed, the hydrogen absorption/desorption temperature of the Mg17Al12-BaO is 181/271 °C, which is 73/37 °C lower than that of the Mg17Al12. Furthermore, the catalytic mechanism of BaO on the hydrogenation of Mg17Al12 (110) surface is investigated by density functional theory (DFT). Calculations indicate that compared with the Mg17Al12 (110) surface, the adsorption energy and dissociation barrier of hydrogen on the Mg17Al12-BaO (110) surface are both improved significantly. Our experimental and theoretical results are helpful for understanding the effect of metal oxide on hydrogen storage properties of Mg17Al12.