Sustainable Approach to Fabricate High-Performance Symmetry Supercapacitor Electrodes from Natural Coconut-Shell-Derived Porous Activated Carbon with Nickel Oxide Nanocomposites

This paper reports high specific capacitance of an activated carbon nickel oxide nanocomposite (PCNiO) electrode that has been synthesized from natural coconut shell using carbonization and an activated PCNiO nanocomposite with the help of a hydrothermal process. The structural phase, chemical change, morphology, and pore structure of the PCNiO nanocomposite were investigated using a variety of techniques including X-ray diffraction (XRD), Fourier transform infrared (FTIR), Brunauer-Emmett-Teller (BET), thermo-gravimetric analysis (TGA), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) techniques. Among the prepared samples, PCNiO-150 displays the most significant characteristics that were used to create symmetric supercapacitors (SSCs). It had a specific capacitance (<i>C</i> _sp) of 598.6 F/g at a scan rate of 10 mV/s. The Galvanostatic charging-discharging (GCD) curves showed a high specific capacitance (<i>C</i> _sp) of 656.2 F/g at a current density (CD) of 1.5 A/g. Additionally, even after 5000 cycles, it had achieved long-term cycle stability with capacitance retention of 78.34% and Coulombic efficiency of 97.55%. Its highest energy density (ED) and power density (PD) were 44 Wh kg^-1 and 562.5 W kg^-1, respectively. Additionally, the fabricated SSC device is serially connected to turn on a commercial green LED for 30-40 s at the time of the experiment. This paper proposes a novel environmentally sustainable and easy-to-use carbon source as well as a cost-effective and technologically unique approach for carbon supercapacitors in environmental applications.