Synergistic catalysis of YF3 and Ni/C: Exceptional effects on hydrogen storage performances of MgH2 at low temperature

Magnesium hydride (MgH 2 ) emerges as a cost-effective and high-capacity hydrogen storage candidate. Despite these advantages, its utilization is constrained by sluggish reaction kinetics and the requirement for elevated operating temperatures. In this study, we aim to address these limitations by investigating the synergistic catalytic effect of yttrium fluoride (YF 3 ) and nickel-loaded nitrogen self-doped porous carbon (Ni/C) as catalysts for MgH 2 . Co-doping with YF 3 and Ni/C reduces the dehydrogenation activation energy to 74.56 kJ/mol, enabling 5.22 wt% H 2 desorption within 5 min at 300 °C. Notably, the system exhibits enhanced low-temperature reaction kinetics, with the MgH 2 -YF 3  + Ni/C composite releasing 5.74 wt% H 2 at 250 °C within 30 min. At 50 °C, the co-doped composite achieves a hydrogen storage capacity of 5.18 wt% within 4 h, whereas the composite with Ni/C only absorbs 3.72 wt% H 2 . Moreover, the MgH 2 -YF 3  + Ni/C shows 98.4 % capacity retention after 30 cycles, indicating excellent reversibility. Mechanistic analysis reveals that the outstanding catalytic performance originates from the synergistic effect among YH 2 /YH 3 , MgF 2 , Mg 2 Ni/Mg 2 NiH 4 , and nitrogen-doped carbon. YH 2 /YH 3 and Mg 2 Ni/Mg 2 NiH 4 act as “hydrogen pump”, providing more active sites for the reaction. Additionally, MgF 2 functions as an electron transfer medium, weakening the Mg-H bond. The introduction of nitrogen self-doped porous carbon improves the dispersion of the catalyst and prevents aggregation, enhancing the dissociation of hydrogen molecules. This work demonstrates a promising strategy for improving the low-temperature hydrogen storage performance of MgH 2 and offers insights into the design of rare-earth fluoride-based catalysts.