Improved Hydrogen Storage Kinetic Properties of MgH₂ with NiO/NiCo(Fe)₂O₄/(Ni)

Abstract

Developing catalysts with exceptional catalytic activity is crucial in solid hydrogen storage. Two catalysts, NiO/NiCo 2 O 4 and NiO/NiFe 2 O 4 /Ni, are successfully prepared and incorporated into MgH 2 for the first time to investigate the hydrogen storage properties of MgH 2 . The experimental results indicate that the hydrogen desorption temperatures for the composites of MgH 2 + 5 wt % NiO/NiCo 2 O 4 (MgH 2 + NC) and MgH 2 + 5 wt % NiO/NiFe 2 O 4 /Ni (MgH 2 + NF) occur at 241 and 175 °C, respectively. Hydrogen desorption of ballmilled MgH 2 begins at 272 °C. Both MgH 2 + NF and MgH 2 + NC exhibit excellent hydrogen absorption kinetics. At 150 °C and 3 MPa, MgH 2 + NF and MgH 2 + NC can absorb 5.93 and 5.95 wt % of H 2 in as little as 1 min, respectively. The desorption activation energies of MgH 2 + NF and MgH 2 + NC are 88.38 and 81.56 kJ/mol, respectively, compared to pure MgH 2 , which has an E a of 181.4 kJ/mol. Furthermore, cycle experiments demonstrate that both MgH 2 + NC and MgH 2 + NF display excellent cycle stability, maintaining hydrogen storage capacities of approximately 99.8 and 98%, respectively, after 10 cycles. In situ formed Fe extends the defect structure and interfaces with MgH 2 , thus providing additional hydrogen diffusion channels. Moreover, the embedded clusters of Mg 2 NiH 4 /Mg 2 CoH 5 function as "multistage hydrogen pumps", providing surface pathways for efficient hydrogen absorption. This study offers experimental evidence and novel insights aimed at enhancing the kinetic performance of MgH 2 for hydrogen storage.