LiBH4 Nanoconfined in Porous Hollow Carbon Nanospheres with High Loading, Low Dehydrogenation Temperature, Superior Kinetics, and Favorable Reversibility

Lithium borohydride (LiBH4), with a high hydrogen capacity of 18.5 wt %, is an ideal candidate for hydrogen storage; however, it suffers from high thermal stability, low kinetics, and poor reversibility. Nanoconfinement is an effective strategy to tackle these problems, but a main drawback of nanoconfined systems is the low loading fraction of LiBH4, which leads to a low theoretical hydrogen capacity of the systems. It is thus highly desired to design scaffolds with high porosity and a reasonable pore structure for achieving high loading of LiBH4. In this work, porous hollow carbon nanospheres (PHCNSs) with uniform size, high specific surface area, large pore volume, and reasonable pore structure are delicately designed and controllably synthesized as the scaffold for confining LiBH4. The as-prepared PHCNSs can accommodate up to 70 wt % LiBH4, while the system still shows a low dehydrogenation temperature of ca. 200 °C and releases rapidly 8.1 wt % H2 at 350 °C within 25 min. Such a high loading of LiBH4 and high dehydrogenation capacity at a low temperature have never been reported to date based on our knowledge of carbon-based nanoconfined LiBH4 systems. Moreover, the system with 60 wt % LiBH4 shows favorable reversibility and rapid hydrogenation under moderate conditions. The morphology and structure evolutions of the confined systems during cycling are investigated, and the mechanism of the improved hydrogen storage property is proposed. The present work provides further insight into rationally utilizing porous carbon scaffolds with a well-designed structure to improve the hydrogen storage performance of LiBH4.