Synergistic effect of nitrogen and oxygen self-doping in bio-waste derived activated carbon for supercapacitor applications

Abstract

As the demand for sustainable energy solutions grows, the development of eco-friendly, high-performance electrode materials is crucial for advancing supercapacitor technologies. Bio-waste derived carbon-based materials have gained significant interest due to their abundance, low cost, and environmental benefits. In this study, nitrogen and oxygen self-doped activated carbon, obtained from wood apple shells, was synthesized and systematically prepared for supercapacitor applications. The carbonization and activation processes are carried out using potassium hydroxide in a nitrogen atmosphere at 800 °C, resulting in activated carbon with an exceptionally high specific surface area of 1351.93m²g^-1. The structural analysis conducted through Raman spectroscopy identified structural defects that enhance electrical conductivity, whereas Fourier-transform infrared spectroscopy (FTIR) validated the presence of hydroxyl, carboxyl, and ketonic groups that facilitate faradaic reactions. X-ray photoelectron spectroscopy (XPS) further elucidated the effective self-doping with nitrogen and oxygen, which produced a synergistic effect, significantly enhancing the charge storage capabilities. Scanning electron microscopy (SEM) highlighted a highly porous structure, favorable for efficient ion exchange and rapid electrochemical kinetics. Electrochemical evaluations in a three-electrode system demonstrated specific capacitances of 483.1 F g⁻¹ in 6 M KOH and 218.1 F g⁻¹ in 1 M Na₂SO₄ at 3 A g⁻¹, underscoring the material's robust performance in both electrolytes. Moreover, a symmetric supercapacitor employing this material retains 83 % of capacitance retention following 5000 cycles, showcasing remarkable practical relevance. These findings highlight the potential of wood apple shell-derived activated carbon as a sustainable, high-performance material for next-generation energy storage systems.