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.