Highly Dual-Heteroatom-Doped Ultrathin Carbon Nanosheets with Expanded Interlayer Distance for Efficient Energy Storage

Larger interlayer distance and higher doping efficiency of heteroatoms are considered to be the two most effective solutions to modulate the electronic structure of carbon materials to achieve improved electrochemical storage performances. Here, an innovative popping process is applied to puff biomaterials, i.e., the Chinese five grains of round-grained rice and wheat, into aerogels using the traditional Chinese popcorn machine. Thus, well-defined and interconnected three-dimensional pores are constructed within the biomaterial-derived carbon aerogels after a one-step pyrolysis process. As a result, the interlayer distance of the carbon nanosheets is slightly expanded from similar to 3.6 to similar to 3.7 angstrom, providing more expanded channels for rapid diffusion and adsorption of heteroatom precursors on the surface of the carbon layers. Therefore, a high amount of nitrogen and sulfur incorporation has been realized in the pyrolyzed carbon nanosheets, which further expand the interlayer distance between the carbon layers from similar to 3.7 to similar to 4.0 angstrom. These N, S dual-doped carbon nanosheets, derived from both rice and wheat, display outstanding energy storage performances, thus demonstrating the general ability or possibility of the traditional Chinese popping strategy to convert other biomaterials into similar carbon nanosheets with expanded interlayer distance and enhanced heteroatom doping efficiency.