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

Magnesium hydride (MgH 2 ) with excellent hydrogen absorption kinetics is important for the wide application of hydrogen energy. Herein, to accelerate the sorption kinetics of MgH 2 and lower its dehydrogenation temperature, we design and prepare a carbon film coated dual transition metal alloy , the Fe 0.64 Ni 0.36 @C composite with a core-shell structure, and employ it as an additive to synthesize MgH 2 –Fe 0.64 Ni 0.36 @C system by ball-milling and hydriding combustion method. In contrast to pure MgH 2 , the initial hydrogen release temperature of the MgH 2 –Fe 0.64 Ni 0.36 @C composite lowers to 250 °C from 378 °C and the composite can absorb 5.18 wt% H 2 within 20 min (150 °C, 3 MPa H 2 ). More importantly, the apparent activation energy of the dehydrogenation for decomposition of Fe 0.64 Ni 0.36 @C-doped MgH 2 reduced from 162.8 ± 8.3 kJ/mol to 86.9 ± 4.6 kJ/mol. The enhanced hydrogen sorption kinetics of MgH 2 –Fe 0.64 Ni 0.36 @C mainly attributes to the synergistic effect between the formed Fe@C and Mg 2 Ni/Mg 2 NiH 4 . Moreover, the MgH 2 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.