Bubbling Chemical Vapors in Molten Metal toward XIV-Group Nanosheets.

Two-dimensional (2D) XIV-group nanosheets (germanene, silicene, and stannene) possess unique physical and chemical features promising in fields of electronics, energy storage, and conversions. However, preparing these nanosheets is challenging owing to their non van der Waals structure with strong chemical bonds inside. Herein, a bubbling chemical-vapor growth method is proposed to synthesize these XIV-group nanosheets by bubbling XIV-group-element chlorides in molten sodium. During the synthetic process, XIV-group materials are formed by the reaction of XIV-group element chlorides with strong reducing sodium, then nucleated, and finally isolated to 2D nanosheets in the gas-liquid interface. With the collapse of vapor bubbles and subsequent injection, 2D nanosheets are continuously produced. The nanosheets (Ge) possess a thickness of ∼3.8 nm and a lateral size of ∼2.0 μm. Combining with graphene, the hybrid and flexible films are obtained, delivering a volumetric specific capacity of 4785 mAh cm^-3 and superior cycling stability (over 4000 cycles) in lithium-ion batteries.