Abstract:Two-dimensional Mo₂TiC₂ MXene material was synthesized by etching Mo₂TiAlC₂ and then doped into MgH₂ to tailor its hydrogen storage performance. The initial hydrogen desorption temperature of the Mo₂TiC₂-doped MgH₂ was significantly reduced from 330 °C (pristine MgH₂) to 187 °C. Isothermal dehydrogenation analysis indicated that the MgH₂+9 wt.% Mo₂TiC₂ composite rapidly discharged 6.4 wt.% H₂ at 300 °C within 4 min. For hydrogenation, the dehydrogenated MgH₂+9 wt.% Mo₂TiC₂ uptook 6.5 wt.% H₂ at 175 °C within 5 min. By calculation, the activation energy for MgH₂+9 wt.% Mo₂TiC₂ was calculated to be (135.6±1.9) kJ/mol for the desorption reaction and (46.1±0.2) kJ/mol for the absorption reaction. After 20 cycles, 1.0 wt.% H₂ was lost for the MgH₂+9 wt.% Mo₂TiC₂ composite. Microstructure analysis results showed that the presence of Mo in Mo₂TiC₂ enhanced the thermal stability of MXene and reduced the amount of active Ti during cycling, leading to poorer catalytic effect of the catalyst compared to Ti₃C₂.

Key words: hydrogen storage performance; magnesium hydride; Mo₂TiC₂ MXene; catalytic mechanism