In-situ formed Ti/TiH2 from exfoliated few-layered Ti3C2Tx as hydrogen pump enhances the hydrogen storage properties of MgH2

Magnesium hydride (MgH 2 ) is broadly‌ deemed as one of the most prospective solid-state hydrogen storage materials. However, its large-scale application is hindered by several drawbacks, including an excessive dehydrogenation temperature (>300 °C), sluggish kinetic behavior, and inevitable agglomeration and growth during cycling. To address these challenges, two-dimensional few-layered laminated‌ titanium carbide catalyst (FL-Ti 3 C 2 T x ) was synthesized via LiF/HCl etching followed by liquid-phase ultrasonic exfoliation. These FL-Ti 3 C 2 T x nanosheets exhibit efficient catalytic activity for MgH 2 hydrogen storage. The incorporation of 5 wt% FL-Ti 3 C 2 T x significantly reduces the initial dehydrogenation temperature of MgH 2 from 325 °C to 199 °C, while enabling the dehydrogenated sample to reabsorb hydrogen at room temperature. The MgH 2  + 5 wt% FL-Ti 3 C 2 T x composite demonstrates remarkable kinetic performance, releasing 6.5 wt% H 2 within 8 min at 300 °C and uptaking 5.49 wt% H 2 within 1 min at 100 °C. Even after 50 cycles of consecutive dehydrogenation and rehydrogenation, the composite retained a hydrogen storage capacity of 6.90 wt%, corresponding to a 95.30 % capacity retention rate. Microstructure analysis and theoretical calculations reveal that the unique lamellar morphology of FL-Ti 3 C 2 T x not only provides abundant active sites and hydrogen diffusion paths, but also effectively suppresses the agglomeration and growth of Mg/MgH 2 matrix during the hydrogen absorption and desorption. More importantly, the in-situ formed Ti/TiH 2 functions as a “hydrogen pump” accelerating hydrogen diffusion, prolonging the Mg H bond length, and weakening the interaction between Mg and H. These factors synergistically enhance the absorption/desorption kinetics of MgH 2 .