Catalytic effects of nano-sized TiC additions on the hydrogen storage properties of LiAlH4

The catalytic effect of TiC nanopowder addition in varying proportions on the hydrogen storage properties of LiAlH4 has been investigated by pressure-composition-temperature (PCT) experiments, thermo-gravimetry (TG), and differential scanning calorimetry (DSC). The results indicate that doped samples are able to dehydrogenate at much lower temperatures; for example, the onset of dehydrogenation is 85 C for LiAlH4-2 mol% TiC, and the majority of hydrogen (similar to 6.9 wt.%) can be released by 188 C. About 5 out of 6.9 wt.% of H-2 can be released in the range of 85-138 degrees C (heating rate 4 C min(-1)). Isothermal desorption results at 115 degrees C reveal that doped alanate exhibits dehydriding rate 7-8 times faster than that of pure LiAlH4. DSC measurements indicate that enthalpies of decomposition in LiAlH4 decrease significantly with doping. From Kissinger analysis, the apparent activation energies are estimated to be 59 kJ/mol, 70 kJ/mol and 99 kJ/mol for the decompositions of LiAlH4, Li3AlH6 and LiH, respectively. The results of first rehydrogenation indicate that 5 mol% dopant exhibits the maximum absorption of about 1.9 wt.%. XRD, FESEM, EDS, FTIR, and XPS analyses are utilized to put forward a possible catalytic mechanism of nano-sized TiC in ameliorating the dehydriding/rehydriding characteristics of doped LiAlH4. (C) 2010 Elsevier B.V. All rights reserved.