Nanoconfined and <i>in Situ</i> Catalyzed MgH<sub>2</sub> Self-Assembled on 3D Ti<sub>3</sub>C<sub>2</sub> MXene Folded Nanosheets with Enhanced Hydrogen Sorption Performances
Wen Zhu, Li Ren, Chong Lu, Hao Xu, Fengzhan Sun, Zhewen Ma, Jianxin Zou
Abstract
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 Ti3C2Tx 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 Ti3C2Tx (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.