Anions intercalated two-dimension high entropy layered metal oxides for enhanced hydrogen storage in magnesium hydride

Due to the characteristics of large specific surface area, two-dimensional layered materials present spectacular potential for energy-related catalysis. In this work, high entropy layered metal oxides (HELMO) were designed and synthesized to promote the hydrogen storage performance of magnesium hydride (MgH2). The catalytic action of HELMO on MgH2 could be effectively enhanced by modulating the anionic intercalation (NO3/Cl) of the HELMH precursors. Specifically, MgH2 + 10 wt% HELMO-NO3 could dehydrogenate at 184.1 degrees C, and the composite exhibited superior isothermal kinetics with a sharply reduced hydrogen desorption activation energy of 54.59 +/- 3.37 kJ/mol. Moreover, MgH2 + 10 wt% HELMO-NO3 was able to absorb hydrogen at 15.4 degrees C, and the composite charged 5.15 wt% H2 in 50 min at 75 degrees C. For cycling capacity tests, the composite maintained a retention rate of 97.8 % with 6.47 wt% hydrogen capacity after 50 cycles. The catalytic mechanism proposed that layered HELMO wrapped around the MgH2 during ball milling, which not only riveted a large number of heterogeneous active sites on the surface of MgH2, but also effectively inhibited the growth of MgH2 in the process of hydrogen absorption and desorption, ensuring excellent hydrogen storage performance in MgH2.