Improving the Hydrogen Storage Property of Sm_6.5Mg_93.5-TiMn₂ by Accelerating H₂ Dissociation/Recombination and H Diffusion

The development and preparation of composites with multiple active sites and multiple catalytic processes are of great significance for improving the hydrogen storage property of the Mg/MgH2 system. Herein, a TiMn2-type Ti0.90Zr0.10Mn1.30Cr0.40V0.30 hydrogen storage alloy and Sm6.5Mg93.5-x wt % Ti0.90Zr0.10Mn1.30Cr0.40V0.30 (x = 0, 5, 10, and 30) composites were successfully prepared. The TiMn2 hydrogen storage alloy was stable throughout the hydrogen storage performance test. Owing to alloying and hydrogenation-ball-milling, in situ generated Sm3H7 possessed abundant active sites for accelerating H diffusion, and the uniformly distributed TiMn2 hydrogen storage alloy promoted H2 dissociation/recombination in Sm6.5Mg93.5-10 wt % TiMn2 composite. The Sm6.5Mg93.5-10 wt % TiMn2 composite absorbed 4.04 wt % H2 within 3600 s at 373 K and desorbed 4.41 wt % H2 within 500 s at 623 K. The Sm6.5Mg93.5-10 wt % TiMn2 composite exhibited excellent cycling stability with 97.0% retention of hydrogen absorption after 50 hydrogen absorption and desorption cycles. Microstructural analysis showed that Sm3H7 and TiMn2 catalytically active substances were dispersed in the Mg/MgH2 system. The uniformly dispersed Sm3H7 and TiMn2 catalyst afforded the Sm6.5Mg93.5-10 wt % TiMn2 composite with excellent kinetic properties.