KOH-Activated Porous Carbons Derived from Chestnut Shell with Superior Capacitive Performance

Porous carbons (PC) were prepared from a waste biomass named chestnut shell via a two-step method involving carbonization and KOH activation. The morphology, pore structure and surface chemical properties were investigated by scanning electron microscopy (SEM), N-2 sorption, Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The carbons have been evaluated as the electrode materials for supercapacitors by a two-electrode system in 6 mol/L KOH electrolyte. Benefiting from the porous texture, high surface area and high oxygen content, the PCs derived from chestnut shell have exhibited high specific capacitance of 198.2 (PC-1), 217.2 (PC-2) and 238.2 F.g(-1) (PC-3) at a current density of 0.1 A.g(-1), good rate capability of 55.7%, 56.6% and 54.9% in a range of 0.1-20 A.g(-1) and high energy density of 5.6, 6.1 and 6.7 Wh.kg(-1), respectively. This is believed to be due to electric double layer capacitance induced by the abundant micropores and extra pseudo-capacitance generated by oxygen-containing groups. At a power density of 9000 Wh.kg(-1), the energy density is 3.1, 3.5 and 3.7 Wh.kg(-1) for PC-1, PC-2 and PC-3, respectively, demonstrating the potential of the carbons derived from chestnut shells in energy storage devices.