Ni/Co-co-doped Ti2VC2 nanosheets to improve hydrogen storage in MgH2

MgH₂ is one of the most promising materials for solid hydrogen storage and is environmentally friendly primarily owing to its high mass hydrogen storage density (7.6 %). However, the application and development of MgH₂ are limited by its sluggish kinetics, requiring high processing temperatures. In this study, we prepared Ni/Co-co-doped Ti 2 VC 2 bimetallic MXene nanosheets via etching and the hydrothermal method. These nanosheets were then doped into MgH₂, resulting in drastically improved hydrogen storage properties. The MgH₂-based composite hydrogen storage materials doped with 10 wt% Ni/Co–Ti 2 VC₂ (TVCNC) commenced hydrogen emission from 183 °C and could emit 6.65 wt% hydrogen at 300 °C. During the rehydrogenation test, the composites could still absorb hydrogen at 5.0 wt% within a 10 min window at a hydrogen pressure of 20 bar at 125 °C. Moreover, the hydrogen absorption and emission kinetics of the doped MgH₂ were considerably improved. This improvement could be ascribed to the significantly increased specific surface area of the MXene nanosheets after etching, which increased the number of active sites on the surface to accelerate the reaction, thereby accelerating hydrogen adsorption and emission. In addition, the migration of electrons between the multivalent Ti ions as well as between Ni and Co helped accelerate bond cleavage between magnesium and hydrogen, thereby enhancing the kinetic properties. Ni/Co co-doping produced Mg 2 Ni alloys with magnesium via hydrogen adsorption and emission, thus improving the reaction kinetics of the composites.