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Hard carbon has attracted great attention for energy storage owing to low cost and extremely high microporosity, however, hindered by its low electrical conductivity. The common strategy to improve the conductivity is through graphitization process which requires temperatures as high as 3000 °C and inevitably destroys the porous structure. Herein, a balance between the specific surface area and electrical conductivity in a 3D porous hard carbon by in situ iron‐catalyzed graphitization process together with the Si–O–Si network is successfully achieved. The Fe can accelerate the localized graphitization at relatively low temperature (1000 °C) to form nanographite domains with enhanced conductivity, while the Si–O–Si network contributes to generating a 3D porous structure. As a result, the optimized hard carbon exhibits a 3D interconnected and hierarchical porous structure with extremely high specific surface area (2075 m2 g−1) and excellent electrical conductivity (12 S cm−1) which is comparable with that of artificial graphite. And thus, high capacitance of 315 F g−1 and excellent rate capability (174 F g−1 at 40 A g−1) are simultaneously achieved when used as electrodes for supercapacitors. The strategy is promising to build hard carbon materials with well‐tuned properties for high‐performance energy storage. [ABSTRACT FROM AUTHOR]

Large surface area, high conductivity, and rich active site of carbon electrode materials are necessary characteristics for energy storage devices. However, high conductivity and high nitrogen doping of carbon electrode materials are difficult to coordinate. Here, a facile method via the carbonization of nitrogen‐containing Schiff base polymer has been developed to prepare high conductivity and high nitrogen‐doped hierarchical porous carbon. The organic components with a benzene ring structure in the polymer promote the formation of more sp2‐graphitized carbon, which is beneficial for the improvement of electrical conductivity. Nitrogen‐doped hierarchical porous carbon calcined at 900°C under the NH3 atmosphere possesses high nitrogen content of 7.48 at%, a large specific surface area of 1613.2 m2/g, and high electrical conductivity of 2.7 S/cm. As electrode materials in an aqueous‐based supercapacitor, nitrogen‐doped hierarchical porous carbon exhibits superior specific capacitance of 385 F/g at 1 A/g as well as excellent rate performance (242 and 215 F/g at a current density of 100 and 200 A/g, respectively). In addition, the specific capacitance of electrode measured in a two‐electrode system is 335 F/g at 1 A/g, and the long‐term cycling stability can be achieved with more than 94% initial capacitance after 10 000 cycles. The constructed symmetric supercapacitor delivers high energy density and high power density. The outstanding electrochemical performances combined with the novel and scalable synthetic approach make the nitrogen‐doped hierarchical porous carbon potential electrode material for electrochemical devices. [ABSTRACT FROM AUTHOR]