Improve hydrogen sorption kinetics of MgH2 by doping carbon-encapsulated iron-nickel nanoparticles

Magnesium hydride (MgH2) with excellent hydrogen absorption kinetics is important for the wide application of hydrogen energy. Herein, to accelerate the sorption kinetics of MgH2 and lower its dehydrogenation temperature, we design and prepare a carbon film coated dual transition metal alloy, the Fe0.64Ni0.36@C composite with a core-shell structure, and employ it as an additive to synthesize MgH2–Fe0.64Ni0.36@C system by ball-milling and hydriding combustion method. In contrast to pure MgH2, the initial hydrogen release temperature of the MgH2–Fe0.64Ni0.36@C composite lowers to 250 °C from 378 °C and the composite can absorb 5.18 wt% H2 within 20 min (150 °C, 3 MPa H2). More importantly, the apparent activation energy of the dehydrogenation for decomposition of Fe0.64Ni0.36@C-doped MgH2 reduced from 162.8 ± 8.3 kJ/mol to 86.9 ± 4.6 kJ/mol. The enhanced hydrogen sorption kinetics of MgH2–Fe0.64Ni0.36@C mainly attributes to the synergistic effect between the formed Fe@C and Mg2Ni/Mg2NiH4. Moreover, the MgH2 co-doped with the multiple in-situ formed active particles shows excellent cycling performance, indicative of potential application in practical hydrogen storage in the near future.