Conversion of toxic waste to wealth: Diesel soot carbon electrode for sodium-hybrid capacitor

In recent years, hybrid capacitors have proven to be an efficient technology in storing energy faster and at a higher energy capacity while utilizing a renewable source. Herein, we report diesel soot derived from automobile exhausts as a carbon source for all carbon sodium-ion hybrid capacitors. To achieve this, a simple synthesis method was used, followed by activation to significantly increase its charge storing capabilities. The high porosity of this activated diesel soot carbon allows us to achieve high charge storage capacity both as anode and cathode, while increased graphitization with interlayer expansion by heat-treatment technique allows us to obtain greater rate performance combined with superior cycle stability. As a result, activated diesel soot carbon could earn double the capacity as compared to pure diesel soot carbon with specific capacities of 198 and 78 mAhg⁻¹ as anode and cathode, respectively. Full-cell assembly as a hybrid capacitor with carbon as both cathode and anode could deliver a maximum energy density of 97 Whkg⁻¹ and a maximum power density of 10,000 Wkg⁻¹ with cycle stability for 50,000 cycles. This article emphasizes the waste-to-wealth technique in active materials for energy storage devices more extensively.