Abstract: Porous carbons have become the main contender of electrode materials for double-layer capacitors. Carbon materials used in supercapacitors usually require a large specific surface area, high electrical conductivity and efficient ion transport paths. However, such characteristics are usually incompatible in a single carbon material, which greatly restricts the capacitive performance of carbon-based capacitors. Herein, we deve-lop a simple and cost-efficient strategy to convert K2FeO4-impregnated biomass precursor into highly graphitized porous carbons (GPC) with hie-rarchical pores by a one-pot heat-treatment. K2FeO4 works as both a pore-forming agent and graphitization catalyst to fulfill the synchronous hie-rarchical pore generation and graphitization of the skeleton. The resultant GPC material has a large specific surface area (1 257.7 m2·g-1) and a highly graphitized skeleton structure, which solves the competitive relationship in a single carbon material. Benefiting from these unique features, the GPC sample presents superior electrochemical capacitive performance in various aqueous electrolytes (KOH, H2SO4 and Na2SO4). The GPC electrode exhibits satisfactory specific capacitances of 354.8, 323.9 and 188.7 F·g-1in H2SO4, KOH and Na2SO4 electrolytes, respectively. Meanwhile, the assembled GPC-based symmetric capacitors also achieve superb capacitive properties in KOH and Na2SO4 electrolytes, including high capacitance, superior rate capability, high energy density and prominent cycling stability. In addition, our proposed strategy not only alleviates the environmental pollution caused by discarded biowaste, but also obtains high-added-value carbon-based electrodes for supercapacitors in energy storage. Therefore, it demonstrates an example of trash-to-treasure transformation, boosting the utilization of abundant biowaste resources.
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