Constructing graphene nanosheet-supported FeOOH nanodots for hydrogen storage of MgH₂

Novel graphene-supported FeOOH nanodots (FeOOH NDs@G) were successfully prepared by a facile hydrothermal method and doped into MgH₂ through mechanical ball-milling. MgH₂ with 10wt% FeOOH NDs@G began to release hydrogen at 229.8°C, which is 106.8°C lower than that of pure MgH₂. The MgH₂–10wt% FeOOH NDs@G composite could reversibly absorb 6.0wt% hydrogen at 200°C under a 3.2 MPa hydrogen pressure within 60 min. With the addition of FeOOH NDs@G, the dehydrogenation and hydrogenation activation energy of MgH₂ was decreased to 125.03 and 58.20 kJ·mol⁻¹ (156.05 and 82.80 kJ·mol⁻¹ for pure MgH₂), respectively. Furthermore, the hydrogen capacity of the FeOOH NDs@G composite retained 98.5% of the initial capacity after 20 cycles, showing good cyclic stability. The catalytic action of FeOOH NDs@G towards MgH₂ could be attributed to the synergistic effect between graphene nanosheets and in-situ formed Fe, which prevented the aggregation of Mg/MgH₂ particles and accelerated the hydrogen diffusion during cycling, thus enabling the MgH₂–10wt% FeOOH NDs@G composite to exhibit excellent hydrogen storage performance.