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For the first time, few-layer Ti3C2T x (FL-Ti3C2T x ) supporting highly dispersed nano-Ni particles with an interconnected and interlaced structure was elaborated through a self-assembly reduction process. FL-Ti3C2T x not only acts as a supporting material but also self-assembles with Ni2+ ions through the electrostatic interaction, assisting in the reduction of nano-Ni. After ball milling with MgH2, Ni30/FL-Ti3C2T x (few-layer Ti3C2T x supported 30 wt % nano-Ni via self-assembly reduction) shows superior catalytic activity for MgH2. For example, MgH2-5 wt % Ni30/FL-Ti3C2T x can release approximately 5.83 wt % hydrogen within 1800 s at 250 °C and absorb 5 wt % hydrogen within 1700 s at 100 °C. The combined effects of finely dispersed nano-Ni in situ-grown on FL-Ti3C2T x , large specific area of FL-Ti3C2T x , multiple-valence Ti (Ti4+, Ti3+, Ti2+, and Ti0) derived from FL-Ti3C2T x , and the electronic interaction between Ni and FL-Ti3C2T x can explain the superb hydrogen storage performance. Our results will attract more attention to the elaboration of the metal/FL-Ti3C2T x composite via self-assembly reduction and provide a guideline to design high-efficiency composite catalysts with MXene in hydrogen storage fields.

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A sandwich-like Ti 3 C 2 /TiO 2 (A)-C prepared through a facile gas-solid method was doped into MgH 2 by ball milling. Ti 3 C 2 /TiO 2 (A)-C shows a far superior catalytic effect on the hydrogen storage of MgH 2 than individual Ti 3 C 2 or TiO 2 (A)-C, assigning as a synergistic catalysis between Ti 3 C 2 and TiO 2 (A)-C. For example, the peak dehydrogenation temperature of MgH 2 -5 wt% Ti 3 C 2 /TiO 2 (A)-C is reduced to 308 °C, much lower than that of MgH 2 -5 wt% Ti 3 C 2 (340 °C) or MgH 2 -5 wt% TiO 2 (A)-C (356 °C). After dehydrogenation, the dehydrogenated MgH 2 -5 wt% Ti 3 C 2 /TiO 2 (A)-C can uptake approximately 4 wt% of hydrogen within 800 s at 125 °C, while for the dehydrogenated MgH 2 -5 wt% Ti 3 C 2 and MgH 2 -5 wt% TiO 2 (A)-C, only 3 wt% and 2.65 wt% hydrogen content can be obtained, respectively. Besides this, MgH 2 -5 wt% Ti 3 C 2 /TiO 2 (A)-C exhibits the lowest apparent activation energies (42.32 kJ mol −1 H 2 for the hydrogen absorption and 77.69 kJ mol −1 H 2 for the hydrogen desorption), which can explain the excellent hydrogen ab/desorption kinetic properties. The synergetic effects between the special layered structure and multiple valence titanium compounds (Ti 4+ , Ti 3+ , Ti 2+ , Ti 0 ) verified by the x-ray photoelectron spectroscopy results are responsible for the catalytic mechanism on the hydrogen storage of MgH 2 . This study also supplies innovative insights into designing high efficiency MXene derivative catalysts in hydrogen storage.