NaAlH4 dehydrogenation properties enhanced by MnFe2O4 nanoparticles

The catalytic effects of MnFe2O4 nanoparticles on the dehydrogenation properties of NaAlH4, prepared by ball milling, are investigated. The onset temperatures for NaAlH4 + 7 mol% MnFe2O4 are 95 °C, 152 °C and 327 °C for the three dehydrogenation steps, significantly lower compared with as-received NaAlH4. The isothermal dehydriding kinetics shows that adding MnFe2O4 to NaAlH4 could significantly enhance the desorption kinetics of NaAlH4, 7 mol% MnFe2O4-doped sample also displays the well-maintained kinetics and only a slight capacity loss for the three cycles. From the differential scanning calorimetry and the Kissinger desorption kinetics analysis, the apparent activation energy of the 7 mol% MnFe2O4-doped sample for the three steps is 57.74 kJ mol−1, 75.06 kJ mol−1 and 117.22 kJ mol−1, resulting in 56.05 kJ mol−1, 67.53 kJ mol−1 and 59.12 kJ mol−1 reduction, respectively, compared with the as-received NaAlH4. Based on the Fourier Transform Infrared Spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy, Fe0.9536O and amorphous Mn or Mn-containing species together play a synergistic role in remarkably improving NaAlH4 dehydriding properties.