Efficient hydrogen absorption and dehydrogenation of synergistically catalyzed Mg10Fe by MoS2 and Y2O3 via one-step synthesis and multistage regulation

Abstract

To effectively deal with the long preparation period and low hydrogen absorption capacity issue of Mg-based hydrogen storage materials. One-step multistage control strategy and high-pressure hydrogenation have been employed to prepare Mg10Fe-M (M = MoS2 or Y2O3 or both) composites. The phase composition, microstructure, morphology, non-isothermal dehydrogenation thermodynamics and isothermal dehydrogenation kinetics at different milling time (2, 4, 8 h) were explored, and the catalytic hydrogen absorption and discharge mechanism of Mg10Fe–MoS2–Y2O3 was proposed. The addition of MoS2 nanoflowers and Y2O3 powder can synergistically regulate and improve the hydrogenation capacity and dehydrogenation temperature of Mg10Fe. The hydrogen absorption and dehydrogenation of Mg10Fe–MoS2–Y2O3 in short time milling for 2 h are 3.64 wt% and 3.27 wt% respectively. After extending the milling time to 8 h, the thermodynamic and kinetic behavior of Mg10Fe-M (M = MoS2 or Y2O3 or both) is greatly improved. Kinetically, the hydrogenation or dehydrogenation capacity increases significantly, Mg10Fe–MoS2 doesn't need activation, and the hydrogenation capacity reaches 5.42 wt% at 623 K, with a yield of about 85.9 % in 60 min. Thermodynamically, the initial dehydrogenation peak temperature drops to about 310 °C, and the apparent activation energy also decreases significantly, among which Mg10Fe–MoS2–Y2O3 was 91.87 kJ/mol. These are attributed to the fact that MoS2 nanoflowers provide many active sites for H2 adsorption and H atom dissociation. Synchro-efficient synthesis and regulation of Mg-rich composite hydrogen storage materials are expected to shorten the synthesis cycle, improve the hydrogen storage performance, and lay a material foundation for the design and development of solid hydrogen storage devices.