Unleashing Superior Hydrogen Storage of Magnesium Hydride via Vanadium-Doped Bimetallic MXene.

Magnesium hydride (MgH2) has been recognized as a promising hydrogen storage material because of its low cost and high hydrogen capacity. However, the sluggish kinetics and high operating temperature hindered its utilization. Herein, vanadium-substituted titanium-based bimetallic MXene (Ti3-nVnC2) was prepared to boost the hydrogen storage efficiency of MgH2. The incorporation of 5 wt % Ti2.2V0.8C2 dramatically decreased the dehydrogenation temperature of MgH2 and improved its kinetics and cyclic stability. The MgH2-5 wt % Ti2.2V0.8C2 started to release hydrogen at 165 °C, and it released 7.0 wt % H2 in 30 min at 220 °C and took in 5.3 wt % H2 in 2 h at 75 °C, showing excellent kinetics. In addition, the activation energy of MgH2-added Ti2.2V0.8C2 was 80.81 ± 3.29 kJ mol-1, which is lower than that of the most Ti-/or V-based catalyst-doped MgH2 systems. Mechanism analysis reveals that the remarkably enhanced hydrogen storage performance is ascribed to the stable existence and uniform distribution of Ti-species (Ti0 and Titanium hydride) and V-species (V0 and V5+), which facilitated the rapid hydrogen absorption/desorption of MgH2 and ensured its stable hydrogen storage capacity. This study offers valuable perspectives for the assembly and design of bimetallic catalysts within the realm of solid-state hydrogen storage materials.