Nanolayer-like-shaped MgFe2O4 synthesised via a simple hydrothermal method and its catalytic effect on the hydrogen storage properties of MgH2

Abstract

In this study, the effect of nanolayer-like-shaped MgFe₂O₄ that is synthesised via a simple hydrothermal method on the performance of MgH₂ for hydrogen storage is studied. MgH₂ + 10 wt% MgFe₂O₄ is prepared by using the ball milling method. The MgFe₂O₄-doped MgH₂ sample started to release H₂ at approximately 250 °C, 90 °C and 170 °C lower than the milled and pure MgH₂ respectively. At 320 °C, the isothermal desorption kinetic study has shown that the doped sample has desorbed approximately 4.8 wt% H₂ in 10 min while the milled MgH₂ desorbed less than 1.0 wt% H₂. For isothermal absorption kinetics, the doped sample can absorb approximately 5.5 wt% H₂ in 10 min at 200 °C. Meanwhile, the undoped sample absorbs only 4.0 wt% H₂ in the same condition. The activation energy of 10 wt% MgFe₂O₄-doped MgH₂ composite is 99.9 kJ mol⁻¹, which shows a reduction of 33.1 kJ mol⁻¹ compared to the milled MgH₂ (133.0 kJ mol⁻¹). X-ray diffraction spectra display the formation of new species which are Fe and MgO after dehydrogenation, and these new species are believed to act as the real catalyst that plays a crucial role in improving the sorption performance of the MgFe₂O₄-doped MgH₂ system by providing a synergetic catalytic effect.