Peanut shell-derived activated carbon incorporated with nitrogen anode and cobalt cathode materials (“two-in-one” strategy) for asymmetric supercapacitor (N-PAC//PVA-KOH//Co-PAC) applications

Abstract

Supercapacitors have received more attraction in energy storage technology owing to their low cost, high capacity, and good stability. Herein, a bio-mass-derived carbon source is prepared from peanut shells and incorporated with heteroatom boron (B-PAC), nitrogen (N-PAC), and metal oxide (cobalt oxide (Co-PAC)). The structural and surface morphology of the obtained PACs is studied using X-ray diffraction (XRD) and Raman spectroscopy, scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis. The electrochemical behavior of PAC-coated electrodes is evaluated through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge study (GCD). Compared to boron, the nitrogen heteroatom enhances electric double capacitance up to 302 F g⁻¹ at 2 A g⁻¹. Moreover, cobalt oxide exhibits a synergetic effect with the carbon matrix to boost electrochemical-specific capacitance behavior, and the capacitance value is 295 F g⁻¹ at 1 A g⁻¹ in the three-electrode system. Asymmetric supercapacitor devices were made using N-PAC as the negative electrode and Co-PAC as the positive electrode. The N-PAC//PVA-KOH//Co-PAC device delivers 45 W h kg⁻¹ energy density and 846 W kg⁻¹ at 1 A g⁻¹ power density with 100% capacitance retention after 3000 cycles. The higher energy and power density and long cycle life of the N-PAC//PVA-KOH//Co-PAC device render it as a potential energy storage device for practical applications.