Effect of ternary transition metal sulfide FeNi₂S₄ on hydrogen storage performance of MgH₂

Hydrogen storage is a key link in hydrogen economy, where solid-state hydrogen storage is considered as the most promising approach because it can meet the requirement of high density and safety. Thereinto, magnesium-based materials (MgH₂) are currently deemed as an attractive candidate due to the potentially high hydrogen storage density (7.6 wt%), however, the stable thermodynamics and slow kinetics limit the practical application. In this study, we design a ternary transition metal sulfide FeNi₂S₄ with a hollow balloon structure as a catalyst of MgH₂ to address the above issues by constructing a MgH₂/Mg₂NiH₄-MgS/Fe system. Notably, the dehydrogenation/hydrogenation of MgH₂ has been significantly improved due to the synergistic catalysis of active species of Mg₂Ni/Mg₂NiH₄, MgS and Fe originated from the MgH₂-FeNi₂S₄ composite. The hydrogen absorption capacity of the MgH₂-FeNi₂S₄ composite reaches to 4.02 wt% at 373 K for 1 h, a sharp contrast to the milled-MgH₂ (0.67 wt%). In terms of dehydrogenation process, the initial dehydrogenation temperature of the composite is 80 K lower than that of the milled-MgH₂, and the dehydrogenation activation energy decreases by 95.7 kJ·mol^–1 compared with the milled-MgH₂ (161.2 kJ·mol^–1). This method provides a new strategy for improving the dehydrogenation/hydrogenation performance of the MgH₂ material.