Understanding the effect of polypyrrole and poly(3,4-ethylenedioxythiophene) on enhancing the supercapacitor performance of NiCo2O4 electrodes

Abstract

Herein, two of the most well-known conducting polymers (CP), polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), were coated onto mesoporous NiCo₂O₄ nanosheet arrays through an efficient and controllable electrodeposition process. We considered such a unique nanostructure to be an ideal model to accurately compare and understand the effects of PPy and PEDOT on electrochemical performances. Comparing the electrochemical performances of NiCo₂O₄@CP and pure NiCo₂O₄ electrodes, we found that the NiCo₂O₄@PPy electrode possesses the highest areal capacitance of 4.1 F cm⁻² at 2 mA cm⁻², which is significantly higher than the values obtained for the NiCo₂O₄@PEDOT (0.86 F cm⁻²) and NiCo₂O₄ electrodes (0.65 F cm⁻²). For rate capability, even at a high current density of 30 mA cm⁻², an areal capacitance of 2.7 F cm⁻² can be achieved for the NiCo₂O₄@PPy electrode. Moreover, the NiCo₂O₄@PPy electrode shows considerably smaller equivalent series resistance (ESR) than that of the NiCo₂O₄@PEDOT and NiCo₂O₄ electrodes. Therefore, the NiCo₂O₄@PPy hybrid composites are considered to be ideal supercapacitor electrode materials with enhanced electrochemical performances, which makes them suitable for many practical applications.