Effect of BiVO 4 additive on the hydrogen storage properties of MgH 2

Abstract The MgH2 with 16.7 wt.% BiVO4 composite prepared by ball milling method presented favorable thermodynamic and kinetic performances, and the effect of BiVO4 on the hydrogen storage properties of MgH2 was investigated. The onset desorption temperature of the composite is 538 K, 98 K lower than that of the as-milled MgH2. The composite releases 1.1 wt.% hydrogen at 573 K within 1200 s, while pristine MgH2 hardly release hydrogen under identical conditions. Moreover, the composite absorbs 1.99 wt.% hydrogen at 423 K, 2.12 times than that of pristine MgH2. The dehydrogenation activation energy of MgH2 is reduced from 122.29 kJ/mol to 84.33 kJ/mol with the addition of BiVO4. The BiVO4 additive also facilitates the H diffusion and alters the rate-controlling step of MgH2 in the hydrogen absorption process. It may be believed that the active V-containing species formed during the dehydrogenation process would greatly improve the hydrogen storage performances of MgH2.