文摘
The catalytic effects of MnFe2O4 nanoparticles on the dehydrogenation properties of NaAlH4, prepared by ball milling, are investigated. The onset temperatures for NaAlH4聽+聽7聽mol% MnFe2O4 are 95聽掳C, 152聽掳C and 327聽掳C for the three dehydrogenation steps, significantly lower compared with as-received NaAlH4. The isothermal dehydriding kinetics shows聽that adding MnFe2O4 to NaAlH4 could significantly enhance the desorption kinetics of NaAlH4, 7聽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聽mol% MnFe2O4-doped sample for the three steps is 57.74聽kJ聽mol鈭?, 75.06聽kJ聽mol鈭? and 117.22聽kJ聽mol鈭?, resulting in 56.05聽kJ mol鈭?, 67.53聽kJ聽mol鈭? and 59.12聽kJ聽mol鈭? 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.