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

Developing catalysts with exceptional catalytic activity is crucial in solid hydrogen storage. Two catalysts, NiO/NiCo2O4 and NiO/NiFe2O4/Ni, are successfully prepared and incorporated into MgH2 for the first time to investigate the hydrogen storage properties of MgH2. The experimental results indicate that the hydrogen desorption temperatures for the composites of MgH2 + 5 wt % NiO/NiCo2O4 (MgH2 + NC) and MgH2 + 5 wt % NiO/NiFe2O4/Ni (MgH2 + NF) occur at 241 and 175 °C, respectively. Hydrogen desorption of ball-milled MgH2 begins at 272 °C. Both MgH2 + NF and MgH2 + NC exhibit excellent hydrogen absorption kinetics. At 150 °C and 3 MPa, MgH2 + NF and MgH2 + NC can absorb 5.93 and 5.95 wt % of H2 in as little as 1 min, respectively. The desorption activation energies of MgH2 + NF and MgH2 + NC are 88.38 and 81.56 kJ/mol, respectively, compared to pure MgH2, which has an Ea of 181.4 kJ/mol. Furthermore, cycle experiments demonstrate that both MgH2 + NC and MgH2 + 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 MgH2, thus providing additional hydrogen diffusion channels. Moreover, the embedded clusters of Mg2NiH4/Mg2CoH5 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 MgH2 for hydrogen storage.