Superior Kinetic and Cyclic Performance of a 2D Titanium Carbide Incorporated 2LiH + MgB₂ Composite toward Highly Reversible Hydrogen Storage

Abstract

Reactive hydride system of 2LiH + MgB2/2LiBH4 + MgH2 is of great potential as hydrogen storage material due to its high theoretical hydrogen storage capacity. However, it suffers from sluggish dehydrogenation/hydrogenation kinetics and poor cyclic stability. In the present study, with the incorporation of a 2D MXene phase of Ti3C2 to the 2LiH + MgB2 mixture by ball milling followed by an initial hydrogenation, the system is hydrogenated to 2LiBH4 + MgH2 and shows superior hydrogen storage kinetics and cyclic stability. 9.0 wt % H2 is released at 400 °C within 20 min. The dehydrogenation product can be highly hydrogenated at 350 °C/10 MPa in less than 5 min. The incorporation of 2D Ti3C2 not only leads to an in situ formation of superfine and well dispersive nanosized TiB2 during the ball milling and initial hydrogenation, which serves as heterogeneous nucleation sites for the dehydrogenation product of MgB2, but also helps reduce the particle size of the system during the milling. The synergetic effect of them improves significantly the hydrogen storage kinetics and the reversibility of the system.