Improving the Hydrogen Storage Property of Sm<sub>6.5</sub>Mg<sub>93.5</sub>-TiMn<sub>2</sub> by Accelerating H<sub>2</sub> Dissociation/Recombination and H Diffusion

The\ndevelopment and preparation of composites with multiple active\nsites and multiple catalytic processes are of great significance for\nimproving the hydrogen storage property of the Mg/MgH<sub>2</sub> system.\nHerein, a TiMn<sub>2</sub>-type Ti<sub>0.90</sub>Zr<sub>0.10</sub>Mn<sub>1.30</sub>Cr<sub>0.40</sub>V<sub>0.30</sub> hydrogen storage\nalloy and Sm<sub>6.5</sub>Mg<sub>93.5</sub>-<i>x</i> wt\n% Ti<sub>0.90</sub>Zr<sub>0.10</sub>Mn<sub>1.30</sub>Cr<sub>0.40</sub>V<sub>0.30</sub> (<i>x</i> = 0, 5, 10, and 30) composites\nwere successfully prepared. The TiMn<sub>2</sub> hydrogen storage\nalloy was stable throughout the hydrogen storage performance test.\nOwing to alloying and hydrogenation-ball-milling, in situ generated\nSm<sub>3</sub>H<sub>7</sub> possessed abundant active sites for accelerating\nH diffusion, and the uniformly distributed TiMn<sub>2</sub> hydrogen\nstorage alloy promoted H<sub>2</sub> dissociation/recombination in\nSm<sub>6.5</sub>Mg<sub>93.5</sub>-10 wt % TiMn<sub>2</sub> composite.\nThe Sm<sub>6.5</sub>Mg<sub>93.5</sub>-10 wt % TiMn<sub>2</sub> composite\nabsorbed 4.04 wt % H<sub>2</sub> within 3600 s at 373 K and desorbed\n4.41 wt % H<sub>2</sub> within 500 s at 623 K. The Sm<sub>6.5</sub>Mg<sub>93.5</sub>-10 wt % TiMn<sub>2</sub> composite exhibited excellent\ncycling stability with 97.0% retention of hydrogen absorption after\n50 hydrogen absorption and desorption cycles. Microstructural analysis\nshowed that Sm<sub>3</sub>H<sub>7</sub> and TiMn<sub>2</sub> catalytically\nactive substances were dispersed in the Mg/MgH<sub>2</sub> system.\nThe uniformly dispersed Sm<sub>3</sub>H<sub>7</sub> and TiMn<sub>2</sub> catalyst afforded the Sm<sub>6.5</sub>Mg<sub>93.5</sub>-10 wt %\nTiMn<sub>2</sub> composite with excellent kinetic properties.