Catalytic Effects of Decorating AlV<sub>3</sub> Nanocatalyst on Hydrogen Storage Performance of Mg@Mg<sub>17</sub>Al<sub>12</sub> Nanocomposite: Experimental and Theoretical Study
Xiubo Xie, Yongcheng Li, Ming Chen, Miaomiao Hu, Yaxin Feng, Jiaxiang Shang, Tong Liu
Abstract
Constructing uniformly coated Mg nanoparticles (NPs) with the addition of the Al–V alloy nanocatalyst and retaining the stability of the core@shell structure are challenging issues. In this work, a novel Mg@Mg17Al12 nanocomposite of 120 nm decorated with Al3V (5 nm) NPs is prepared by the hydrogen plasma metal reaction method. After the first hydrogenation process at 673 K, the Mg17Al12 shell of 3 nm disproportionates into an Al shell and MgH2 core, while Al3V changes into AlV3 and Al. After the hydrogenation/dehydrogenation cycle, the Mg17Al12 shell is obtained again, whereas AlV3 remains unchanged. The nanocomposite can quickly uptake 5.0 wt % H2 within 30 min at 473 K, and the hydrogen absorption capacities of the nanocomposite are almost stable at 6.3 wt % above 473 K. It can release 4.0 wt % H2 within 10 min at 573 K. The apparent activation energies for hydrogen absorption and desorption are decreased to 43.3 and 44.7 kJ/mol H2. The AlV3 nanocatalyst can store hydrogen of 1.0 wt % at 473 K, and the first-principles calculation also implies that the hydrogen dissociation energy on the AlV3 surface is 0.76 eV, much lower than Mg (0.92 eV). Both experimental and calculation results prove AlV3 to be a novel and effective nanocatalyst.