Improved Hydrogen Storage Performance of MgH2-LiAlH4 Composite by Addition of MnFe2O4

The catalytic effects of MnFe2O4 nanoparticles on the hydrogen storage properties of MgH2-LiAlH4, prepared by ball milling, are studied for the first time. The hydrogen storage properties and reaction mechanism are investigated by pressure-composition-temperature (PCT), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The nonisothermal desorption results show that MgH2-LiAlH4 + 5 mol % MnFe2O4 has a lower onset dehydrogenation temperature, 85, 50, and 40 degrees C lower than these of ball-milled MgH2-LiAlH4 sample for each stage in the dehydrogenation process. The isothermal dehydriding kinetics and isothermal rehydrogenation kinetics results indicate that adding MnFe2O4 to MgH2-LiAlH4 could significantly enhance the absorption/desorption kinetics of MgH2-LiAlH4. From the differential scanning calorimetry and Kissinger analysis, the apparent activation energy of the 5 mol % MnFe2O4-doped sample for the three decomposition stage is 55.8, 70.8, and 96.5 kJ/mol, resulting in a 45.7, 85.5, and 99.6 kJ/mol decrease, respectively, compared with the MgH2-LiAlH4 sample. These improvements are mainly attributed to in situ formed Fe0.872O phase and the amorphous Mn-containing phase during the dehydrogenation process, which act as the real catalyst in the MgH2-LiAlH4 + 5 mol % MnFe2O4 composite.