Catalytic effect of double transition metal sulfide NiCo₂S₄ on hydrogen storage properties of MgH₂

The limited practicality of magnesium hydride (MgH₂) is due to its remarkable thermodynamic steadiness and sluggish hydrogen (H₂) storage rate. In this study, NiCo₂S₄, a double transition metal sulfide, was synthesized and used to promote the kinetic properties of MgH₂. Starting release temperature of MgH₂- 10 NiCo₂S₄ composite is 203 °C. MgH₂-10 NiCo₂S₄ composite releases 6.11 wt% H₂ in 5 min at 325 °C, and absorbs 5.54 wt% H₂ in 1 min at 150 °C. Besides, the Arrhenius equation yields the activation energy (E_a) of MgH₂-10 NiCo₂S₄ composite to be 86.50 ± 2.00 kJ/mol. It is noteworthy that the MgH₂-10 NiCo₂S₄ composite generated MgS, Mg₂Ni and Mg₂Co in situ active species during the first dehydrogenation process. The synergistic effect between the MgS, Mg₂Ni/Mg₂NiH₄ and Mg₂Co/Mg₂CoH₅ multiphase catalytic systems was generated in the cycle, which observably boosted the kinetics of Mg/MgH₂.