Enhanced hydrogen storage properties of LiAlH4 catalyzed by CoFe2O4 nanoparticles

The catalytic effects of CoFe2O4 nanoparticles on the hydrogen storage properties of LiAlH4 prepared by ball milling were investigated. The onset desorption temperature of the LiAlH4 + 2 mol% CoFe2O4 sample is 65 degrees C, which is 90 degrees C lower that of the as-received LiAlH4, with approximately 7.2 wt% hydrogen released at 250 degrees C. The isothermal desorption results show that for the 2 mol% CoFe2O4 doped sample dehydrogenated at 120 degrees C, 6.8 wt% of hydrogen can be released within 160 min, which is 6.1 wt% higher than that of the as-received LiAlH4 under the same conditions. Through the differential scanning calorimetry (DSC) and the Kissinger desorption kinetics analyses, the apparent activation energy, Ea, of the 2 mol% CoFe2O4 doped sample is calculated as 52.4 kJ mol(-1) H-2 and 86.5 kJ mol(-1) H-2 for the first two decomposition processes. This is 42.4 kJ mol(-1) H-2 and 86.1 kJ mol(-1) H-2 lower compared with the pristine LiAlH4, respectively, indicating considerably improved dehydrogenation kinetics by doping the CoFe2O4 catalyst in the LiAlH4 matrix. From the Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses, a series of finely dispersed Fe and Co species with a range of valence states, produced from the reactions between LiAlH4 and CoFe2O4, play a synergistic role in remarkably improving LiAlH4 dehydrogenation properties. The rehydrogenation properties of the LiAlH4 + 2 mol% CoFe2O4 sample have also been investigated at 140 degrees C under 6.5 MPa pressure held for 2.5 h.