MXene-supported VHx nanoparticles enhancing hydrogen storage properties of magnesium hydride

With its high mass density, excellent cyclic stability, and low cost, magnesium hydride (MgH2) presents a highly attractive profile for solid-state hydrogen storage, establishing it as a leading candidate in the field. Nevertheless, the commercialization of MgH2 has been hindered owing to its insufficient kinetic performance and elevated operating temperature. In this work, a vanadium hydride nanoparticle (VHx) adhered to Ti3C2 composite catalyst was synthesized by ball milling method to improve the hydrogen storage properties of MgH2. The onset dehydrogenation temperature of the MgH2 + 10wt% VHx@Ti3C2 composite was reduced from 267.6°C to 190.3°C. In addition, MgH2 + 10wt% VHx@Ti3C2 composite could release 6.72wt% hydrogen within 10 min at 290°C. By comparison, MgH2 started to release hydrogen at 267.6°C, whereas a mere 0.29wt% of hydrogen was released under the same condition. After 20 cycles, it could still retain over 95% of its initial hydrogen absorption and desorption capacity, which indicated that MgH2 + 10wt% VHx@Ti3C2 composite exhibited good cycling performance. Investigation of the catalytic mechanism demonstrated that the layered structure of Ti3C2 served as the matrix supplied a great quantity of active sites and VHx functioned as a “hydrogen pump” to accelerate the migration of H ions, thereby facilitating the hydrogen absorption and desorption processes of MgH2, leading to enhanced hydrogen storage properties of MgH2. This work provides a viable strategy for designing vanadium-based catalysts to improve solid-state hydrogen storage materials.