Nanoconfined and in Situ Catalyzed MgH2 Self-Assembled on 3D Ti3C2 MXene Folded Nanosheets with Enhanced Hydrogen Sorption Performances

MXenes are considered as potential support materials for nanoconfinement of MgH₂/Mg to improve the hydrogen storage properties. However, it has never been realized so far due to the stacking and oxidation problems caused by unexpected surface terminations (-OH, -O, etc.) on MXenes. In this study, hexadecyl trimethylammonium bromide was used to build a 3D Ti₃C₂T_x architecture of folded nanosheets to reduce the stacking risk of flakes, and a bottom-up self-assembly strategy was successfully applied to synthesize ultradispersed MgH₂ nanoparticles anchored on the surface of the annealed 3D Ti₃C₂T_x (Ti-MX). The composite with a 60 wt % loading of MgH₂ NPs, 60MgH₂@Ti-MX, starts to decompose at 140 °C and is capable of releasing 3.0 wt % H₂ at 150 °C within 2.5 h. In addition, a reversible capacity up to 4.0 wt % H₂ was still maintained after 60 cycles at 200 °C without obvious loss in kinetics. In situ high-resolution TEM observations of the decomposition process together with other analyses revealed that the nanosize effect caused by the nanoconfinement and the multiphasic interfaces between MgH₂(Mg) and Ti-MX, especially the in situ formed catalytic TiH₂, were main reasons accounting for the superior hydrogen sorption performances.