Effects of SWNT and metallic catalyst on hydrogen absorption/desorption performance of MgH₂

The microstructure and absorption/desorption characteristics of composite MgH₂ and 5 wt % as-prepared single-walled carbon nanotubes (MgH ₂-5ap) obtained by the mechanical grinding method were investigated. Experimental results show that the MgH₂-5ap sample exhibits faster absorption kinetics and relatively lower desorption temperature than pure MgH₂ or MgH₂-purified single-walled carbon nanotube composite. Storage capacities of 6.0 and 4.2 wt % hydrogen for the MgH ₂-5ap composite were achieved in 60 min at 423 and 373 K, respectively. Furthermore, its desorption temperature was reduced by 70 K due to the introduction of as-prepared single-walled carbon nanotubes (SWNTs). In addition, the different effects of SWNTs and metallic catalysts contained in the as-prepared SWNTs were also investigated and a hydrogenation mechanism was proposed. It is suggested that metallic particles may be mainly responsible for the improvement of the hydrogen absorption kinetics, and SWNTs for the enhancement of hydrogen absorption capacity of MgH₂.