Partial carbonization of NiMOF for enhancing the hydrogen sorption/desorption performance of MgH2

Hydrogen is a clean, high-energy-density carrier crucial for carbon neutrality, but its practical use is limited by efficient storage. Magnesium hydride (MgH 2 ) is promising for solid-state storage due to its ultra-high capacity (∼7.6 wt%) and environmental benignity, yet hindered by high operating temperatures (>623 K) and sluggish sorption kinetics. This work develops a flower-like NiMOF@C catalyst to improve MgH 2 's low-temperature performance and cyclic stability. In this work, a series of NiMOF-derived catalytic materials with a distinctive spherical flower-like morphology were synthesized by regulating the reaction temperature during the NiMOF fabrication process. The experimental results unequivocally demonstrated that the obtained NiMOF@C exhibited outstanding catalytic performance. This superior activity is primarily ascribed to its hierarchical flower-like microstructure, featuring a complex internal framework and abundant meso-macroporous cavities, which collectively contribute to a significantly enlarged specific surface area and a high density of accessible active sites. Among all the prepared composites, the MgH 2 sample incorporating 5 wt% NiMOF@C manifested the most pronounced hydrogen storage behavior, maintaining excellent kinetics even under relatively mild thermodynamic conditions. Specifically, at 423 K and 2.6 MPa, the composite achieved a maximum hydrogen uptake of 6.47 wt%, with a rapid absorption of 6.03 wt% H 2 within 10 min. Moreover, it exhibited remarkable reversibility, preserving 97.8% of its absorption and 97.4% of its desorption capacity after 20 consecutive cycles. Notably, the desorption activation energy (E de ) of MgH 2 –5 wt% NiMOF@C was substantially reduced to 91.03 kJ/mol, in sharp contrast to the 181.4 kJ/mol observed for pristine MgH 2 , confirming the pronounced catalytic effect of the NiMOF-derived carbonaceous phase.