Effects of CNTs on the hydrogen storage properties of MgH2 and MgH2-BCC composite

MgH2 with 10 wt.% Ti0.4Mn0.22Cr0.1V0.28 alloy (termed the BCC alloy for its body centred cubic structure) and 5 wt.% carbon nanotubes (CNTs) were prepared by planetary ball milling, and its hydrogen storage properties were compared with those of the pure MgH2 and the binary mixture of MgH2 and the BCC alloy. The sample with CNTs showed considerable improvement in hydrogen sorption properties. Its temperature of desorption was 125 °C lower than for the pure sample and 59 °C lower than for the binary mixture. In addition, the gravimetric capacity of the ternary sample was 6 wt.% at 300 °C and 5.6 wt.% at 250 °C, and it absorbed 90% of this amount at 150 s and 516 s at 300 °C and 250 °C, respectively. It can be hypothesised from the results that the BCC alloy assists the dissociation of hydrogen molecules into hydrogen atoms and also promotes hydrogen pumping into the Mg/BCC interfaces, while the CNTs facilitate access of H-atoms into the interior of Mg grains.