From nanorods to nanoparticles: Morphological engineering enables remarkable hydrogen storage by lithium borohydride

Nanostructured LiBH4 with greatly improved de-/hydrogenation thermodynamics and kinetics has been attracting the ever-growing interest for on-board hydrogen storage applications. However, it is challenging to controllably fabricate various nanostructures of LiBH4 due to its strong reducibility, high chemical activity and sensitivity to water and oxygen. Here, we demonstrate the very first success in tailoring the nanoscaled LiBH4 morphology from nanorods to nanoparticles by using few-layer graphenes (FL-Grs) as supporters. The presence of 30 wt% FL-Grs is optimal because it contributes not only substantial nucleation sites for LiBH4 nanoparticles but also sufficient catalytic activity for hydrogen storage in LiBH4. The resultant LiBH4-30 wt% FL-Grs displays 20-50 nm-sized particles in morphology, which enables the complete reversible storage of 7.2 wt% H2 starting from 230 degrees C for desorption and 190 degrees C for absorption along with a stable cyclability, greatly superior to pristine sample and even the nano-LiBH4/FL-Grs mixture. The somewhat particle growth as well as the segregation and isolation of B and LiH with cycling is reasonably responsible for the gradually slowed desorption/absorption kinetics. This important insight guides the design and development of nanostructured LiBH4-based composites featured high capacity and long life by combining nanometer size effect and catalytic effect.