Achieving superior energy storage and microwave absorption by simultaneously-controlling active heteroatoms and porosities in carbon nanosheets

Abstract Tailoring the carbon-electrode with rich porosities and heteroatoms has been demonstrated to break the limitation of capacitive storage and microwave absorption, but the balance between them remains a great challenge, resulting in the difficulty to control and utilize the active sites. Here, porous heteroatoms co- and tri-doping carbon nanosheets are easily achieved by a developed melting-pressing-carbonization (MPC) approach with the assistance of g-C3N4, which concurrently activates pore structure and surface properties by serving as structure-directing agent, activating agent and nitrogen resource. The optimized co-doping carbon nanosheet (NPCN-1) exhibits a novel surface structure containing high N (14.1%) contents with well-distributing conductive and redox-active N species, and ions-matched pores centered on 0.7 nm, which provides rich-effective active sites to capture fast electron and ion transport, reflected by the energy storage dynamics. Therefore, the NPCN-1 supplies a large specific areal capacitance of 0.434 F m-2, even outperforming the graphene (0.21 F m-2) as supercapacitor electrode, and displays a broad effective absorption bandwidth of 6.64 GHz and a strong reflection loss of -44.5 dB in microwave absorption (MA). These energy storage and MA capability can be further enhanced after realizing tri-doping of O, N and Fe2O3 by MPC strategy, shedding light on an avenue to future application and development for the active materials.