Remarkable capacitive behavior of a Co3O4–polyindole composite as electrode material for supercapacitor applications

Abstract

In this paper, we demonstrate a single step synthesis of cobalt oxide – conducting polyindole (Co₃O₄–Pind) composites by in-situ cathodic electrodeposition. The structural and morphological changes of the as-prepared Co₃O₄–Pind composites have been investigated using various techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman analysis and X-ray photoelectron spectroscopy (XPS). Very interestingly, polyindole decoration over Co₃O₄ results in concomitant change in morphology leading to substantial improvement in the supercapacitor behavior. The electrochemical performance of Co₃O₄–Pind has been investigated by cyclic voltammetry, galvanostatic charge–discharge cycling and impedance analysis. The specific capacitance (SC) of Pind decorated Co₃O₄ is found to be 1805 F g⁻¹ at a current density of 2 A g⁻¹ with excellent rate capability (SC: 1625 F g⁻¹ at a high current density of 25 A g⁻¹) and cycling stability. This remarkable supercapacitive performance of the Co₃O₄–Pind composite is mainly attributed to the synergism that evolved between Co₃O₄ and Pind. More importantly, these electrodes are free from binders and conductive carbon which have significant impact over the gravimetric energy density of the devices.