Facile synthesis of nickel and cobalt oxide-integrated 3-D porous nitrogen-doped carbon derived from Psidium guajava (PNDC/NiCo2O4) for supercapacitor applications

Abstract

In this experimental investigation, porous N-doped carbon (AC) was developed from rotting guavas (Psidium guajava), followed by doping with nickel and cobalt oxide spinel, and was studied for its supercapacitive behaviour. The components of the chemical activators have been varied in a methodical synthesis, and their effects on morphological, physiochemical, and electrochemical characteristics have been examined. Two distinct morphologies of the doped biochars and successful NiCo₂O₄ deposition on them were examined by SEM analysis. AC-CO₃ showed the highest specific surface area SSA (722.56 m² g⁻¹) of all the samples with an average pore diameter of 3.38 nm. X-ray diffraction patterns were in accordance with the band gap energy (E_g) found from Taucs plot, validating the formation of different crystallite-sized spinel NiCo₂O₄ on the biochar. The electrochemical tests like cyclic voltammetry, galvanostatic charge–discharge studies, electrochemical impedance tests and stability tests were carried out in 1 (M) KOH electrolyte, and the areal capacitance from GCD for AC-CO₃MO, MO, AC-ClMO, AC-CO₃, and AC-Cl, respectively, was 761.9, 631.5, 380.5, 499.0, and 223.7 mF cm⁻² at 0.5 mA cm⁻² current density. The better-performing material among them, AC-CO₃MO, exhibits energy densities of 15.77 and 2.05 mW h cm⁻², as well as power densities of 100.14 and 4002.98 mW cm⁻² at 0.5 and 20 mA cm⁻² current densities, respectively. As a result, this study showcases the application of biowaste in energy storage devices along with the impact of the usage of various chemical activators in the synthesis of PNDC and their electrochemical behaviour in supercapacitor applications.