Improved hydrogen desorption in lithium alanate by addition of SWCNT–metallic catalyst composite

A LiAlH ₄/single walled carbon nanotube (SWCNT) composite system was prepared by mechanical milling and its hydrogen storage properties investigated. The SWCNT – metallic particle addition resulted in both a decreased decomposition temperature and enhanced desorption kinetics compared to pure LiAlH ₄. The decomposition temperature of the 5 wt.% SWCNT-added LiAlH ₄ sample was reduced to 80 °C and 130 °C for the first and second stage, respectively, compared with 150 °C and 180 °C for as-received LiAlH ₄. In terms of the desorption kinetics, the 5 wt.% SWCNT-added LiAlH ₄ sample released about 4.0 wt.% hydrogen at 90 °C after 40 min dehydrogenation, while the as-milled LiAlH ₄ sample released less than 0.3 wt.% hydrogen for the same temperature and time. Differential scanning calorimetry measurements indicate that enthalpies of decomposition in LiAlH ₄ decrease with added SWCNTs. The apparent activation energy for hydrogen desorption was decreased from 116 kJ/mol for as-received LiAlH ₄ to 61 kJ/mol by the addition of 5 wt.% SWCNTs. It is believed that the significant improvement in dehydrogenation behaviour of SWCNT-added LiAlH ₄ is due to the combined influence of the SWCNT structure itself and the catalytic role of the metallic particles contained in the SWCNTs. In addition, the different effects of the SWCNTs and the metallic catalysts contained in the SWCNTs were also investigated, and the possible mechanism is discussed.