Peanut shell-derived nickel cobalt oxide@carbon and activated carbon for high-energy supercapacitor electrodes

The concept of employing green technology for energy applications is appealing and increasingly necessary as fossil fuels continue to deplete. This study investigates the use of sustainable carbon-based materials derived from peanut shell extracts and incorporated into a nickel cobalt oxide (NiCo₂O₄) matrix through a green synthesis route for high-performance supercapacitor applications. The resulting NiCo₂O₄@C composite combines the strengths of its components while mitigating their individual limitations. Synthesis parameters, particularly duration, were optimized to improve specific capacity and cycling stability, resulting in samples synthesized over different time frames. Structural and compositional analyses confirmed the successful formation of crystalline spinel NiCo₂O₄ integrated with defect-rich amorphous carbon, while morphological characterization revealed that the 4 hour synthesized NiCo₂O₄@C possessed a porous architecture with abundant cavities and uniformly distributed elements, contributing to its superior electrochemical performance. An asymmetric supercapacitor device assembled using NiCo₂O₄@C @4 h as the positive electrode and activated carbon (AC) derived from the residual biomass as the negative electrode, delivered a specific energy of 38 Wh kg^-1 and a specific power of 712 W kg^-1 at 1 A g^-1. Notably, this approach enables 100% utilization of peanut shell biomass, offering a cost-effective and scalable solution for high-performance energy storage with minimal environmental impact.