Catalytic effects of multiple heterointerfaces on the hydrogen storage properties of magnesium hydride

The application and further industrialization of magnesium hydride (MgH₂) are restricted by its intrinsically high de-hydrogenation temperature and dragged kinetics though it is believed as one of the most encouraging solid-state hydrogen storage materials with considerable capacity. Herein, a bimetallic layered MXene VNbC, which was mixed with MgH₂ by high energy ball milling, was obtained by etching compact layered MAX VNbAlC with HF. The beginning de-hydrogenation temperature of the as-prepared MgH₂ blended with 10 wt% VNbC (denoted as MgH₂-10 VNbC) composites was excitingly 170 °C and it exhibited faster kinetics and excellent cycling stability. Additionally, compared with the Nb₂C or V₂C doped MgH₂, the bimetallic MXene VNbC doped MgH₂ showed a synergistic effect which could uptake 2.0 wt% H₂ even at ambient temperature within 60 min. Impressively, the as-prepared MgH₂-10 VNbC could release 6.0 wt% of H₂ at 250 °C within 480 s with de-hydrogenation activation energy of only 73.18 kJ/mol H₂. The remarkable hydrogen storage performance could be put down to the in-situ formed NbH_x/Nb, fast electron transfer between different states of V and MgH₂/VNbC/NbH_x heterointerfaces. Additionally, the finely dispersed VNbC provided MgH₂ with abundant attachment sites and limited agglomeration of MgH₂ during cycling. This work highlights the indispensable role of heterointerfaces tailoring Mg-based hydrogen storage materials.