Electropolymerized polypyrrole nanocomposites with cobalt oxide coated on carbon paper for electrochemical energy storage

Polypyrrole (PPy)/cobalt oxide (Co3O4)/carbon paper (CP) ternary composites prepared by potentiodynamic electropolymerization of pyrrole monomers onto flower-like Co3O4 (f-Co3O4) nanoparticles coated on CP (PPy/f-Co3O4/CP) were studied serving as electrode materials for supercapacitor applications. The f-Co3O4 with unique porous morphology on CP was first obtained by drop casting Co3O4 ethanol suspensions onto CP. Ball-like Co3O4 (b-Co3O4) with dense structure was also prepared for comparison. The electrochemical results including cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) in 2.0 M KOH aqueous solution revealed that the PPy/Co3O4/CP ternary composites exhibited superior supercapacitive performances than both f-Co3O4/CP and b-Co3O4/CP. Specifically, a specific capacitance of 398.4 F/g was obtained for the PPy/f-Co3O4/CP, much higher than that of 40.9 and 22.0 F/g for f-Co3O4/CP and b-Co3O4/CP, respectively. The electrochemical impedance spectroscopy studies suggested that better capacitive properties in PPy/f-Co3O4/CP were attributed to the pseudocapacitive contributions from the PPy nanocoating and greatly reduced charge transfer resistance in the composites. PPy/f-Co3O4/CP also displayed an excellent cycling stability with negligible capacitance loss after 1000 cycles. (C) 2015 Elsevier Ltd. All rights reserved.