Catalytic effect of sandwich-like Ti3C2/TiO2(A)-C on hydrogen storage performance of MgH2.

A sandwich-like Ti3C2/TiO2(A)-C prepared through a facile gas-solid method was doped into MgH2 by ball milling. Ti3C2/TiO2(A)-C shows a far superior catalytic effect on the hydrogen storage of MgH2 than individual Ti3C2 or TiO2(A)-C, assigning as a synergistic catalysis between Ti3C2 and TiO2(A)-C. For example, the peak dehydrogenation temperature of MgH2-5 wt% Ti3C2/TiO2(A)-C is reduced to 308 °C, much lower than that of MgH2-5 wt% Ti3C2 (340 °C) or MgH2-5 wt% TiO2(A)-C (356 °C). After dehydrogenation, the dehydrogenated MgH2-5 wt% Ti3C2/TiO2(A)-C can uptake approximately 4 wt% of hydrogen within 800 s at 125 °C, while for the dehydrogenated MgH2-5 wt% Ti3C2 and MgH2-5 wt% TiO2(A)-C, only 3 wt% and 2.65 wt% hydrogen content can be obtained, respectively. Besides this, MgH2-5 wt% Ti3C2/TiO2(A)-C exhibits the lowest apparent activation energies (42.32 kJ mol-1 H2 for the hydrogen absorption and 77.69 kJ mol-1 H2 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 (Ti4+, Ti3+, Ti2+, Ti0) verified by the x-ray photoelectron spectroscopy results are responsible for the catalytic mechanism on the hydrogen storage of MgH2. This study also supplies innovative insights into designing high efficiency MXene derivative catalysts in hydrogen storage.