Superior Catalytic Effect of Nickel Ferrite Nanoparticles in Improving Hydrogen Storage Properties of MgH2

The catalysis of NiFe2O4 nanoparticles on the hydrogen storage performances of magnesium hydride synthesized by high-energy ball milling was studied for the first time. The H-2 storage performances and catalytic mechanism were studied by pressurecompositiontemperature (PCT), differential scanning calorimetry (DSC), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The nonisothermal dehydrogenation results display that the initial dehydrogenation temperature of 7 mol % NiFe2O4-doped MgH2 is 191 degrees C, which is 250 degrees C lower than that of pristine MgH2. The desorption kinetics displays that the MgH2+7 mol % NiFe2O4 sample could desorb 3.79 wt % H-2 within 1 h at 300 degrees C under H-2 pressure of 0.1 MPa. The absorption kinetics displays that the MgH2+7 mol % NiFe2O4 sample could absorb 2.06 wt % H-2 within 3 h near room temperature under H-2 pressure of 4 MPa. The desorption activation energy of the MgH2+7 mol % NiFe2O4 sample is 59.6 kJ/mol, decreasing 195.3 kJ/mol as compared with pristine magnesium hydride. The reaction enthalpy and entropy of the MgH2+7 mol % NiFe2O4 sample during the dehydrogenation process are improved. The enhancement in the H-2 storage performances of MgH2 by adding NiFe2O4 nanoparticles is primarily ascribed to intermetallic Fe7Ni3 and (Fe,Ni) phases during the desorption procedure, which act as the real catalyzer in the 7 mol % NiFe2O4-doped sample.