In-situ TiH/V₈C₇ from bimetallic TiVC MXene for enhanced hydrogen storage in the 2LiBH₄-MgH₂

Catalysis is an effective means to improve the slow kinetics of hydrogen absorption and desorption, as well as the poor cycle life of the 2LiBH₄+MgH₂ composite system. In this study, the TiVC MXene was obtained by etching TiVAlC and introduced into 2LiH + MgB₂ by ball milling. Products obtained were heated and hydrogenated to prepare the 2LiBH₄ + MgH₂ (LMBH) system, which exhibits distinguished kinetic performance and capacity retention rate. In the LMBH + 6 wt% TiVC, a 9.3 wt% hydrogen is released within 35 min at 400 ℃ as well as hydrogenation is completed within 30 min at 350 ℃, 9 MPa. Moreover, the capacity retention rate was up to 96 % after the 15^th cycle. During the heating and hydrogenation process, the TiH and V₈C₇ are generated in-situ as active products, and stably exist in the subsequent process to catalyze the hydrogen absorption-desorption reactions of the composite. The presence of TiH/LiH/V₈C₇/MgB₂ interface improves the kinetic performance of the system. Reversibility is improved by inhibiting the generation of polyborane and the aggregation during the hydrogen absorption-desorption process. The interface structure-activity relationship is first elucidated that between bimetallic MXene and 2LiBH₄ + MgH₂ composite system during hydrogen absorption-desorption processes, providing a novel viewpoint and optimization path for the modification research of 2LiBH₄ + MgH₂ composites.