Carbon-based materials (e.g. activated carbon, graphene, carbon nanotubes, carbon nanofibers), have received great attention as electrode materials for supercapacitors due to their excellent electrical conductivity, large surface area and versatile morphology. However, as electric double layer capacitance (EDLC) materials, the specific capacitances of carbon materials are typically less than 100 F g-1. To enhance the capacitance of carbon-based materials for supercapacitors, many groups focused on doping heteroatom into carbon matrix. For example, using B, N, O, and S dopants to improve the pseudocapacitance based on redox reaction. Moreover, the introduction of O and S dopants can also improve the electrode surface wettability. N doping can facilitate electron transport in carbon lattice. Despite dual and multiple heteroatoms doping further enhance the charge transportation due to their potential synergistic effects, previous studies have mainly been focused on their catalytic applications. The understanding of the multi-doped carbonaceous materials for supercapacitors is very limited. Another effective route to enhance the capacitive performance of carbon-based materials is pore engineering. The engineered pores increase the specific surface area and therefore specific capacitance. Furthermore, the rational design of porous carbon materials, especially 3D multiscale porous structure, could shorten ion diffusion length and optimize rate capability. However, the combination of these elemental doping and pore engineering has rarely been reported. In this work, we precisely fabricated, for the first time, a novel N,O,S tri-doped hierarchical porous carbon foam (NOS-HPC) with high electrical property, good mechanical property, and multiscale pore system composed of macro-, ordered meso-, micro-pores simultaneously. The obtained NOS-HPC three-electrode shows excellent specific capacitance (402.5 F g-1 at 1 A g-1) and high rate capability. Moreover, a symmetric supercapacitor based on our NOS-HPC materials exhibits a fast charging storage feature (with high specific energy density of 13.5 W h kg-1 at a specific power density of 36 kW kg-1) and good stability (with the retention of the initial specific capacitance up to 92% after 20000 cycles). This novel strategy provides a facile platform for designing more metal-free capacitive materials with fine porous structure and diverse heteroatom-doped carbons for high-performance energy storage devices.

Pore engineering and heteroatom doping of carbon foams for ultrafast supercapacitors

2019 Spring National Meeting

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