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
.