The effect of cobalt ferrite (CoFe2O4) nanopowder synthesised through a solvothermal method on the dehydrogenation properties of sodium alanate (NaAlH4) was studied for the first time. The onset decomposition temperature of NaAlH4 is significantly reduced after milling with CoFe2O4, in which the 10 wt% CoFe2O4-doped NaAlH4 sample starts to decompose at ∼100 °C. In contrast, the as-milled NaAlH4 begins to decompose at ∼200 °C, ∼100 °C higher than the doped sample. With respect to desorption kinetic at constant temperature of 150 °C, the 10 wt% CoFe2O4-doped NaAlH4 sample desorbed ∼2.2 wt% hydrogen within 30 min, whereas the as-milled NaAlH4 only desorbed below 0.2 wt% hydrogen. The Kissinger plot exhibited that the apparent activation energy (EA) for hydrogen release from NaAlH4 is significantly reduced after adding with 10 wt% CoFe2O4-doped NaAlH4. The EA values for the first and second stage dehydrogenation of the 10 wt% CoFe2O4-doped NaAlH4 composite are calculated as 80.3 and 88.2 kJ/mol, respectively, and these values are reduced at approximately 34.3 and 30.5 kJ/mol compared with the as-milled NaAlH4 (114.6 and 118.7 kJ/mol, respectively). Based on the X-ray diffraction result, the enhancement of desorption properties of NaAlH4 with the presence of CoFe2O4 is presumably due to the synergistic catalytic effect played by new active species (Co3O4 and Fe) that in situ formed during the desorption process.
- Cobalt ferrite
- Sodium alanate