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

Abstract

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 °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 ℃, and the composite charged 5.15 wt% H₂ in 50 min at 75 ℃. 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.