Symmetric supercapacitor based on Co3O4 nanoparticles with an improved specific capacitance and energy density

Metal oxides have garnered significant research interest as highly effective electrode materials for supercapacitors. In this study, we synthesized Co3O4, an electrode material for supercapacitors, utilizing an in-situ hydrothermal method with varying pH levels in the precursor solution. The obtained samples underwent through structural, optical, surface morphological, electrical, and electrochemical analyses, affirming their exceptional suitability for supercapacitor applications. The influence of pH fluctuations in the synthesis process, on the specific capacitance values were analyzed. The X-ray diffraction pattern and Raman spectrum confirmed the normal cubic spinel structure of Co3O4 nanoparticles. The X-ray photoelectron spectrum revealed the chemical bond states of Co3O4. The optical bandgap have been investigated from the Tauc plot. The surface area and morphology were determined through Brunauer Emmett and Teller method and field emission scanning electron microscope images. A high specific capacitance of 1195.05 Fg−1 at a current density of 1.5 Ag−1 was obtained in the three-electrode study for the sample synthesized at a pH of 10. A symmetric supercapacitor (SSC) device was fabricated to facilitate practical analysis. The symmetric supercapacitor device demonstrated a notably elevated specific capacitance of 870.6 Fg−1 at an operational current density of 5 Ag−1, concurrently achieving an enhanced energy density of 77.3 W h/kg and superior power density of 1997.7 W/kg. These performance metrics surpassed those of prior studies in the field. Furthermore, the SSC device exhibited an excellent cyclic stability of 88 % after undergoing 970 charge/discharge cycles. As a result, Co3O4 emerges as a promising and efficient electrode material for applications in supercapacitors.