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[Display omitted] • NiO/Peanut shell activated carbon (Ni/PSAC) using wet impregnation method. • Ni/PSAC electrode delivered a specific capacitance of 848F g−1 at 8 A g−1. • Asymmetric device reporting energy density of 39.14 Wh kg−1. • For waste-to-effective energy storage, it is an excellent strategy. The approach outlined in this study provides insights into developing sustainable and cost-effective energy storage solutions utilizing agricultural waste materials focusing on using peanut shells to make activated carbon with subsequent impregnation of NiO for supercapacitor electrodes. X-ray diffraction analysis showed the NiO-impregnated peanut shell-activated carbon (Ni/PSAC) nanocomposite material had a face-centered cubic structure. The electrochemical behavior of Ni/PSAC electrode and Ni/PSAC//AC device were comprehensively deliberated through cyclic voltammetry (CV), Galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. The GCD data of Ni/PSAC//AC device uncovered a boosted specific capacitance of 154.63F g−1, accompanied by an energy density of 39.14 Wh kg−1 and a power density of 2700 W kg−1 at 2 A g−1 current density. These findings suggest the potential of mesoporous Ni/PSAC electrode as an efficient and hopped-up material for asymmetric supercapacitor. [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-O-doped Alpinia galanga stem-based carbon nanofiber succesfully synthesis. • The hierarchical porous carbon exhibit high specific surface area of 1065.58 m2/g. • The porous carbon was performed in solid-free binder form. • In 2-electrode system, supercapacitor possessed specific capacitance of 226F g−1. In this study, activated carbon with hierarchical pores and a nanofiber structure doped with oxygen was prepared using a pure biomass-based sustainable strategy involving integrated chemical impregnation and pyrolysis. Alpinia galangal stem was chosen as it functions as fast conductive network with abundant electrochemical active sites for high-grade electrode materials. The optimal precursor exhibited self-doping of oxygen ranging from 6.15 to 15.69 % with 1065.58 m2/g, which contributed to the redox reaction of the electrode material. When tested in a 2-electrode system, the porous carbon nanofibers showed a high specific capacitance of 226F g−1 at 1 A g−1 in 1 M H 2 SO 4 electrolyte, producing an energy density of 9.3483 Wh kg−1 with a coulombic efficiency of 89.01 %. The results showed that oxygen-doped hierarchical porous carbon nanofibers produced from Alpinia galangal stem biomass and designed to be solid-free of binders are highly promising as high-quality electrode materials that can improve sustainable supercapacitor performance. [ABSTRACT FROM AUTHOR]