Bio-waste-derived one-step carbonized hierarchical structured carbon/cobalt oxide composite for energy storage application

A new strategy has been made to investigate low-cost porous carbon electrode material by using bio-waste raw date seeds activated with potassium hydroxide (KOH) to synthesize porous carbon cobalt oxide composite (PCCo) using facile one-step carbonization and to achieve high specific capacitance. The characterization of PCCo composite was done by powder X-ray diffraction, Fourier transform infrared spectrometer, field emission scanning electron microscopy, high-resolution transmission microscopy, Brunauer–Emmett–Teller (BET), and Raman spectroscopy techniques to confirm the chemical changes, morphology, and structural phase. It is observed that there is a high specific surface area (397 m² g⁻¹) and an abundant mesopores for PCCo composite. This hierarchical morphology structure offers good ion/electron transport channels for better electrochemical characteristics. The maximum specific capacitance was found to be 496 F/g at a scan rate of 10 mV/s, and also from the galvanostatic charge–discharge curve, it was 671 F/g at a current density of 1.5 A/g. The fabricated SSC PCCo-0.4//PCCo-0.4 device provides an energy density of 47.4 Wh kg⁻¹ and a power density of 853.2 W kg⁻¹ with a capacitance retention of 84.4% and a coulombic efficiency of 97% even after 5000 cycles. These results suggest that porous carbon composites are cost-effective, technologically unique, and eco-friendly for environmental supercapacitor applications.

Graphical abstract

Scheme: Schematic depicted of the synthesis of PCCo-0.4 composites by one-step carbonization and activation process from date seed and cobalt oxide (Co₃O₄).