Ternary nanocomposite of cobalt oxide nanograins and silver nanoparticles grown on reduced graphene oxide conducting platform for high-performance supercapattery electrode material

The ternary nanocomposite of cobalt oxide (Co₃O₄) and silver (Ag) nanoparticles with reduced graphene (rGO) was successfully synthesized via single-step hydrothermal method and applied as a positrode material in supercapattery. The successful synthesis of ternary nanocomposite (rGO-Co₃O₄–Ag) and uniform distribution of Co₃O₄ nanograins over graphene matrix decorated with Ag nanoparticles was confirmed using X-ray diffraction, field emission scanning electron microscope, energy-dispersive X-ray and X-ray photoelectron spectroscopy. From electrochemical studies such as cyclic voltammetry, galvanic charge-discharge and impedance spectroscopy, it was found that the prepared ternary nanocomposite exhibited excellent performance compared to its counterparts (Co₃O₄, rGO-Co₃O₄). The rGO-Co₃O₄–Ag ternary nanocomposite showed a specific capacity of 94.20 C g⁻¹ that is remarkably higher than the rGO-Co₃O₄ (63.98 C g⁻¹) and Co₃O₄ (58.92 C g⁻¹) in a three-electrode cell system using 1 M KOH electrolyte. The two electrodes cell assembly (supercapattery) was fabricated using rGO-Co₃O₄–Ag nanocomposite as a positrode and activated carbon as a negatrode. The assembled supercapattery (rGO-Co₃O₄–Ag/activated carbon) was able to run in a potential range of 0–1.5 V even at the higher scan rate. The two electrodes cell studies demonstrated that the assembled supercapattery at a current density of 0.6 A g⁻¹ achieved energy density and power density of 23.63 Wh kg⁻¹ and 440 W kg⁻¹ respectively. It also displayed excellent cycling stability with capacity retention around 85.5% after 3000 cycles at a current density of 3 A g⁻¹.