In situ hydrogenolysis-engineered TiC MXenes synergistically enhance hydrogen storage in magnesium.

Two-dimensional (2D) transition metal carbides (a MXene material) have garnered significant attention owing to their exceptional catalytic performance in magnesium-based hydrogen storage systems. However, existing studies on metal-based MXene catalysts have predominantly focused on elucidating how multivalent metal species facilitate hydrogen transport pathways, while largely neglecting the structural configuration, spatial distribution, and mechanistic roles of carbon components within these materials. Herein, we first study the intrinsic mechanism of in situ hydrogenolysis-engineering of representative Ti-based MXene (TiC) systems based on density functional theory (DFT) calculations. Subsequently, these theoretical results are experimentally validated through comprehensive characterization and hydrogen storage performance evaluations for TiC-doped MgH composites that were synthesized via mechanical ball milling under a 40 bar H atmosphere. Key findings reveal that the hydrogen-driven structural reorganization of TiC spontaneously generates graphene-like carbon layers and Ti active species during ball milling. These carbon encapsulations of MgH with doped Ti-containing catalytic species not only effectively inhibit grain agglomeration but also synergistically enhance hydrogen diffusion kinetics. Hence, the dehydrogenation temperature of MgH@TiC decreased from 360 °C to 290 °C compared with pure MgH, while the capacity retention rate increased from 62 % to 97 %. This work addresses the dual roles of MXene for enhancing Mg-based hydrogen storage systems, providing critical insights into the design of efficient catalytical material.