Two-step KOH-activated peanut shell-derived porous carbon for high-performance supercapacitors

With the increasing demand for sustainable energy storage devices, biomass-derived carbon materials have been regarded as promising electrode candidates for supercapacitors because of their renewability, low cost, and environmental compatibility. As abundant agricultural wastes, peanut shells remain largely underutilized; therefore, their conversion into high-value carbon materials is of considerable significance for waste valorization and energy storage applications. In this work, peanut shell-derived porous carbon was prepared by pre-carbonization followed by high-temperature KOH activation. During activation, the carbon skeleton was effectively etched by KOH, generating abundant micropores and a hierarchical pore structure. The optimized PHPC-800-2 exhibits a well-developed multidimensional porous network, a high specific surface area of 1668.77 m 2  g −1 , a total pore volume of 0.69 cm 3  g −1 , and a moderate micropore-to-mesopore ratio, thereby providing abundant active sites and efficient ion transport pathways. Electrochemical tests demonstrate that in a three-electrode system, the PHPC-800-2 electrode delivers a high specific capacitance of 240.65 F g −1 at a current density of 0.5 A g −1 ; when the current density is increased to 5 A g −1 , the specific capacitance is 205.5 F g −1 , still retaining 85.4% of the capacitance, indicating good rate capability. Furthermore, the symmetric supercapacitor assembled based on PHPC-800-2 exhibits a high specific capacitance of 91.6 F g −1 at a current density of 0.5 A g −1 , achieves an energy density of 12.72 Wh kg −1 at a power density of 500 W kg −1 , and retains 99.37% of its capacitance after 20,000 charge-discharge cycles. These results demonstrate that peanut shell waste can be converted into high-performance porous carbon electrodes, providing a sustainable strategy for biomass-derived carbon materials in energy storage applications.