Experimental and theoretical studies on two-dimensional vanadium carbide hybrid nanomaterials derived from V₄AlC₃ as excellent catalyst for MgH₂

Hydrogen is considered one of the most ideal future energy carriers. The safe storage and convenient transportation of hydrogen are key factors for the utilization of hydrogen energy. In the current investigation, two-dimensional vanadium carbide (VC) was prepared by an etching method using V4AlC3 as a precursor and then employed to enhance the hydrogen storage properties of MgH2. The studied results indicate that VC-doped MgH2 can absorb hydrogen at room temperature and release hydrogen at 170 °C. Moreover, it absorbs 5.0 wt.% of H2 within 9.8 min at 100 °C and desorbs 5.0 wt.% of H2 within 3.2 min at 300 °C. The dehydrogenation apparent activation energy of VC-doped MgH2 is 89.3 ± 2.8 kJ/mol, which is far lower than that of additive-free MgH2 (138.5 ± 2.4 kJ/mol), respectively. Ab-initio simulations showed that VC can stretch Mg-H bonds and make the Mg-H bonds easier to break, which is responsible for the decrease of dehydrogenation temperature and conducive to accelerating the diffusion rate of hydrogen atoms, thus, the hydrogen storage properties of MgH2 are remarkable improved through addition of VC.