Excellent catalytic activity of in-situ formed Ti3C2 nanoparticles for boosting hydrogen release from light metal hydride

Abstract

Lithium aluminum hydride (LiAlH₄) exhibits significant potential as a solid-state hydrogen storage medium. However, its practical implementation is restricted by high activation barriers, kinetic limitations, and irreversibility. In this work, a novel solvent-induced phase separation strategy was employed to synthesize TiC@C with excellent catalytic activity, aiming to improve the dehydrogenation performance of LiAlH₄. The addition of 5 wt% TiC@C remarkably reduces the initial hydrogen desorption temperature of LiAlH₄ by 124 °C, decreasing from 164 °C to 40 °C. The composite system achieves rapid hydrogen release with 4.5 wt% H₂ liberated within 2 h at 90 °C and 6.2 wt% H₂ desorbed in merely 20 min at 150 °C. Kinetic analysis indicates significantly reduced activation energies for both dehydrogenation stages, decreasing from 136.5 kJ/mol to 71.6 kJ/mol for the first stage and from 123.6 kJ/mol to 94.2 kJ/mol for the second stage. Multiscale characterizations combining kinetic analysis reveal that the exceptional performance originates from ball milling-induced in-situ formation of Ti₃C₂ phase, which generates numerous favorable nucleation sites for dehydrogenation products. These interfacial structures create abundant heterointerfaces with LiAlH₄. Density functional theory (DFT) calculations reveal that, in different structural states, TiC@C facilitates AlH bond elongation through orbital dehybridization and interfacial electron transfer via Al → Ti charge polarization, thereby significantly lowering the AlH bond dissociation energy barrier in the composite system. These effects change the two-step dehydrogenation models of LiAlH₄, making it easier for hydrogen release and uptake. This interfacial catalysis paradigm establishes new fundamental principles for overcoming kinetic limitations in metal hydride-based hydrogen storage systems through targeted electronic and crystallographic engineering.