Candle soot carbon-Co3O4 nanofibers composite as a binder-free electrode for high-performance supercapacitor application: An experimental and theoretical investigation

Abstract

Extensive research has been conducted on nanostructured metal oxide electrodes for energy storage applications, particularly in supercapacitors, owing to their high specific capacitance. However, a major hindrance to their commercialization is their limited life cycles. To address this issue, incorporating carbon allotropes as a conductive support to enhance the electrode's stability has been explored. In the current work, a novel composite material was synthesized by combining candle soot carbon with cobalt oxide (Co3O4) to create a highly efficient electrode. The optimal composite, with a 2 wt% of candle soot carbon to Co3O4, exhibited utmost specific capacitance (997.5 Fg−1) at 1 Ag−1. After subjecting both electrodes to 10,000 cycles of repetitive charge and discharge, the composite demonstrated a capacitance retention of 83.3 %, while the Co3O4 electrode only achieved 75 % under identical conditions. Additionally, Density Functional Theory (DFT) investigations were performed to elucidate the improved charge-storing capacities of the composite electrode. The computed density of states indicates enrichment of energy states near the Fermi level in the composite when seen to pristine Co3O4. The Partial Density of States (PDOS) analysis illustrates the transportation of charge from the carbon p orbital (candle soot carbon) to the Co d orbital (Co3O4), validating the conductivity improvement in the hybrid configuration, which benefits from enhanced charge storage performance. Overall, the composite material is promising for hybrid supercapacitors, especially due to the incorporation of candle soot carbon as one of its components. It not only enhances the performance of the supercapacitor but also offers the advantage of being a renewable material derived from waste materials. This combination makes the composite an appealing and sustainable choice for next-generation energy storage devices.