NaAlH4 dehydrogenation properties enhanced by MnFe2O4 nanoparticles

Abstract

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.