In this paper, we report amorphous-carbon-supported TiB2 nanoparticles having sizes of 2–4 nm (nano-TiB2@C) as highly active catalysts for hydrogen storage in NaAlH4. Nano-TiB2@C was synthesized by a simple calcination at 550°C with Cp2TiCl2 and MgB2 (molar ratio of 1:1) as precursors. The addition of 7 wt% nano-TiB2@C reduced the onset dehydrogenation temperature of NaAlH4 by 100 to 75°C. A practically available hydrogen capacity of 5.04 wt% could be desorbed at 140°C within 60 min, and completely hydrogenated at 100°C within 25 min under a hydrogen pressure of 100 bar. Notably, the hydrogen capacity was almost unchanged after 20 cycles, which shows the stable cyclability, considerably higher than those of structures catalyzed by Ti halides or TiO2. The stable catalytic function was closely related to the in-situ-formed Ti–Al alloy, which considerably facilitated the dissociation and recombination of H–H and Al–H bondings.
Li–Mg–B–H composite (2LiBH 4 + MgH 2 ) possesses a very high hydrogen storage capacity of 11.4 wt%. However, it still suffers from high operating temperature, slow kinetics, and poor reversibility. In this work, the two-dimensional Ti 3 CN MXene was first synthesized and then introduced into the Li–Mg–B–H composite. The addition of 5 wt% Ti 3 CN reduces the onset dehydrogenation temperature of the 2LiBH 4 + MgH 2 composite by about 50 °C and shortens the induction period of the LiBH 4 decomposition at 400 °C from >90 min to <10 min. The reversible capacity maintains at 8.3 wt% after 20 cycles, with a capacity retention ratio of 93%. Microstructure studies show that Ti 3 CN will partially transform to a highly-dispersed nano-TiB 2 with particle size around 5 nm. Such nano-TiB 2 could serve as an active catalyst to significantly improve the kinetics and reversibility of the Li–Mg–B–H composite. This work offers a strategy to enhancing the hydrogen storage performance of the advanced metal borohydride-based composites by addition of the MXene material and provides some new insights in understanding the role of MXene in tailoring the hydrogen storage properties of the Li–Mg–B–H composite.
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