Using a Self-Assembled Two-Dimensional MXene-Based Catalyst (2D-Ni@Ti₃C₂) to Enhance Hydrogen Storage Properties of MgH₂

Abstract

In this work, we report the remarkable catalytic effects of a novel Ti₃C₂ MXene-based catalyst (Ni@Ti-MX), which was prepared via self-assembling of Ni nanoparticles onto the surface of exfoliated Ti₃C₂ nanosheets. The resultant Ni@Ti-MX catalyst, characterized by ultradispersed Ni nanoparticles being anchored on the monolayer Ti₃C₂ flakes, was introduced into MgH₂ through ball milling. <i>In situ</i> transmission electron microscopy (TEM) analysis revealed that a synergetic catalytic effect of multiphase components (Mg₂Ni, TiO₂, metallic Ti, etc.) derived in the MgH₂ + Ni@Ti-MX composite exhibits remarkable improvements in the hydrogen sorption kinetics of MgH₂. In particular, the MgH₂ + Ni@Ti-MX composite can absorb 5.4 wt % H₂ in 25 s at 125 °C and release 5.2 wt % H₂ in 15 min at 250 °C. Interestingly, it can uptake 4 wt % H₂ in 5 h even at room temperature. Furthermore, the dehydrogenation peak temperature of the MgH₂ + Ni@Ti-MX composite is about 221 °C, which is 50 and 122 °C lower than that of MgH₂ + Ti-MX and MgH₂, respectively. The excellent hydrogen sorption properties of the MgH₂ + Ni@Ti-MX composite are primarily attributed to the peculiar core-shell nanostructured MgH₂@Mg₂NiH₄ hybrid materials and the interfacial coupling effects from different catalyst-matrix interfaces. The results obtained in this study demonstrate that using self-assembling of transition-metal elements on two-dimensional (2D) materials as a catalyst is a promising approach to enhance the hydrogen storage properties of MgH₂.