Desorption Behaviours of Lithium Alanate with Metal Oxide Nanopowder Additives

摘要

The effects of metal oxide nanopowder (Fe2O3, Cr2O3, ZnO and MoO3) additions by dry ball millingon the hydrogen desorption behaviours of LiAlH4 have been investigated. Among them, adding Fe2O3leads to the most pronounced improvement on the onset dehydrogenation temperature and desorptionkinetic rate. The dehydrogenation temperature of the 5 wt.% Fe2O3-doped LiAlH4 sample was reducedto 80 C and 145 C in the first and second stages, respectively, compared with 150 C and 180 C forthe as-received LiAlH4. In terms of the desorption kinetics, the 5 wt.% Fe2O3-doped LiAlH4 samplereleased about 3.8 wt.% hydrogen at 90 C after 60 minutes of dehydrogenation, but all the otherdoped samples released less than 0.7 wt.% hydrogen under the same conditions. From the Kissingerplot based on differential scanning calorimetry at different heating rates, the apparent activation energyof the as-received LiAlH4 was calculated to be 102 and 110 kJ/mol for the first two dehydrogenationsteps, and these values were reduced by 84 and 96 kJ/mol, respectively, after being doped with Fe2O3.Based on the X-ray diffraction and Fourier transform infrared spectroscopy examinations, it is believedthat the significant improvement of LiAlH4 dehydrogenation properties in the Fe2O3-doped sampleswas due to the synergetically catalytic effects of the in-situ generated Li5FeO4 and Fe0.974O that wereformed during the milling process.