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

摘要

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 ℃ and 130 ℃ for the first and second stage, respectively, compared with 150 ℃ and 180 ℃ 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 ℃ 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 calo-rimetry 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 LiAlH4 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.