For most electrodes fabricated with carbon, transition metal compounds, or conductive polymers, the capacitance may deteriorate with cyclic charging and discharging. Thus, an electrochemically stable supercapacitor has long been pursued by researchers. In this work, the hierarchical structure of balsa wood is preserved in the converted carbon which is used as a supporting framework to fabricate electrodes for supercapacitors. Well‐grown carbon nanotubes (CNTs) on interior and exterior surfaces of balsa carbon channels provide two advantages including 1) offering more specific surface area to boost capacitance via electric double layer capacitance and 2) offering more active Fe and Ni sites to participate in the redox reaction to enhance capacitance of the balsa carbon/CNTs electrode. The balsa carbon/CNTs demonstrate an excellent area capacitance of 1940 mF cm−2. As active sites on Ni and Fe catalysts and inner walls of CNTs are gradually released, the capacitance increases 66% after 4000 charge–discharge cycles. This work brings forward a strategy for the rational design of high‐performance biomass carbon coupled with advanced nanostructures for energy storage.

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Metal-organic frameworks—through the use of creative synthetic designs—could produce MOF materials with excellent porosity, stability, particle microstructures, and conductivity, and their inherent characteristics—including their porosity and controllable structure—may result in an immense number of prospects for energy storage. In this paper, a nanosphere-like NiCo-MOF was effectively manufactured via an ultra-fast microwave technique. Additionally, the ideal synthesis conditions of the NiCo-MOF were investigated by adjusting the microwave output power and microwave reaction time. Under the reaction conditions of a 600 W microwave and a 210 s microwave reaction time, the NiCo-MOF exhibited an excellent capacitance of 1348 F/g at a current density of 1 A/g and an 86.1% capacity retention rate at 10 A/g. In addition, self-assembled NiCo-MOF/AC asymmetric capacitors showed a splendid energy density of 46.6 Wh/kg and a power density of 8000 W/kg.

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