Non‐stoichiometric Ni ₃ ZnC _0.7 carbide loading on melamine sponge‐derived carbon for hydrogen storage performance improvement of MgH ₂

Abstract The high operating temperatures and slow kinetics limit the application of MgH 2 ‐based hydrogen storage materials. Here, a composite of Ni 3 ZnC 0.7 /carbon nanotubes loaded onto a melamine sponge‐derived carbon (MS) skeleton is prepared and loaded onto MgH 2 . During dehydrogenation, Ni 3 ZnC 0.7 reacts with MgH 2 and in situ changes to Mg 2 Ni/Zn. The transformation of Mg 2 Ni/Mg 2 NiH 4 serves as a “hydrogen pump”, providing diffusion channels for hydrogen atoms and molecules to promote the de‐/hydrogenation processes. Moreover, Zn/MgZn 2 provides the catalytic sites for the transformation of Mg/MgH 2 . The length of the Mg–H bond is elongated from 1.72 to 1.995 Å, and the dissociation energy barrier of MgH 2 is reduced from 1.55 to 0.49 eV. As a result, MgH 2 with 2.5 wt% MS@Ni 3 ZnC 0.7 can absorb 5.18 wt% H 2 at 423 K within 200 s, and its initial dehydrogenation temperature is reduced to 585 K. After 20 cycles, the dehydrogenation capacity retention is determined to be 94.6%. This work demonstrates an efficient non‐stoichiometric metal carbide catalyst for MgH 2 .