Porous carbon materials have attracted tremendous attention due to their high surface area, large pore volume, high electrical conductivity and diverse surface functions. These features are desired for a broad range of applications, such as water purification, gas absorption, catalysts immobilization and energy storage. A major recent interest has been enhancing energy efficiency and reducing fossil fuel dependence by electrochemical energy storage. Although a vast number of porous carbons have been developed for electrode applications, these devices performance are still limited by their moderate energy or power density, mainly due to the lack of effective carbon architecture. Traditional carbon materials, such as activated carbons (ACs) have high surface area but poor control of porosity and pore connectivity, which leads to decreased energy density at high rates due to large diffusion resistance. Carbon nanotubes (CNTs) networks have large open pores for high-rate charge/discharge but their surface area is insufficient to ensure large capacitance. Although other novel carbons were made that show higher specific capacitance than normal ACs through pore size control under sub-nanometer range, the relatively slow ion diffusion in small pores restricts the power performance.
It has been shown that porous carbons having hierarchical pore structure is a viable design to achieve both high surface area and facile transport kinetics. Herein, we report a new type of microporous carbon made through a low temperature pyrolysis process of an intrinsic 3D hierarchical nanostructured polymeric molecular sieve without any sacrificing template. A conducting polymer molecular sieve was converted into porous carbon by thermal annealing; subsequent chemical activation to further increase the carbon surface area and microporosity without structural collapse, which leads to 3D hierarchical porous carbon (HPC). The microporous carbon shows 3D porous network connected by coral-like nanofibers with diameters of ~100 nm. This polymeric molecular sieve template approach offers several advantages over other previously reported synthetic methodology. With the use of specific crosslinker, the porous network structure is easily tuned; moreover, the raw materials are of low cost, together with the simple synthetic technique, this technique offer wide range of tunability, including pore volume and surface area, in addition to heteroatom doping of nitrogen and other types of metal ions, showing promising electrochemical performance of above 200F/g in aqueous electrolyte and comparable gravimetric capacitance in organic electrolyte.
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