Effect of LiBH4 on hydrogen storage properties of magnesium hydride-carbon composite

In this paper, a magnesium hydride-carbon composite (MgH 2 @CS) was successfully synthesized by hydrogenation, employing magnesium powder and carbonized-starch (CS) as the raw material. The as-prepared MgH 2 @CS was ball-milled with LiBH 4 to constitute a novel Li–Mg–B–H system (2LiBH 4 –MgH 2 @CS). Compared with the primary 2LiBH 4 –MgH 2 , the 2LiBH 4 –MgH 2 @CS composite showed a significant improvement in hydrogen storage performance. Temperature programmed desorption (TPD) analyses show that the 2LiBH 4 –MgH 2 @CS composite starts to slowly release hydrogen at about 150 °C, which is 245 °C lower than that of the pure 2LiBH 4 –MgH 2 ; the final hydrogen desorption capacity reaches 9.3 wt% (LiBH 4 with a weight loss of 7.0 wt%). In particular, the capacity retention rate of 2LiBH 4 –MgH 2 @CS reaches 80.5% after five reversible de/hydrogenation cycles at 400 °C. Microstructure analyses reveal that the CS with lamellar structure could not only serve as a support for anchoring well-dispersed MgH 2 nanoparticles , but could also effectively prevent the aggregation and growth of Mg and magnesium hydrides during de/hydrogenation. Furthermore, the homogeneous nanosized Mg that is generated from decomposition of MgH 2 @CS has high reactivity, which could accelerate the decomposition of LiBH 4 and meanwhile shorten the incubation period of MgB 2 , thereby greatly enhancing the kinetics of dehydrogenation . These studies provide us with fundamental insights into the design of the Li–Mg–B–H system.