Non‐stoichiometric Ni <sub>3</sub> ZnC <sub>0.7</sub> carbide loading on melamine sponge‐derived carbon for hydrogen storage performance improvement of MgH <sub>2</sub>
Ziyin Dai, Ping Wu, Lirong Xiao, Hideo Kimura, Chuanxin Hou, Xueqin Sun, Sijie Guo, Wei Du, Xiubo Xie
Abstract
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 .