Facile synthesis of various Co3O4/bio-activated carbon electrodes for hybrid capacitor device application

Abstract

Constructing functionalized carbons decorated with transition metal oxide is an efficient way to combine the cycling stability and high specific capacitance of electrodes for electric double layer capacitors and pseudocapacitors, and the morphology is undoubtedly a key factor for the electrochemical performance. Here, three activated carbons derived from biomass with different morphologies are obtained by carbonizing rosewood (R), corncob (C) and lotus seedpod (L) waste plant body, and then the bio-activated carbons decorated with Co3O4 are prepared by simple oxidation-precipitation and crystallization method. Among the R, C, L carbons, Co3O4, R-Co3O4, C-Co3O4 and L-Co3O4 composites, the L-Co3O4 composite shows best electrochemical performance. At a scan rate of 5 mV s−1, its specific capacitance reaches 1405.3 F g−1 (975 C g−1 at 1 A g−1). Furthermore, a hybrid capacitor is fabricated using L-Co3O4 as the positive electrode and activated carbon as the negative electrode, resulting in energy density of 23.1 W h kg−1, tremendous power density of 3990.6 W kg−1 and high cycling stability (80.2% retention and coulombic efficiency of 98.8% after 5000 cycles). The equipped hybrid supercapacitor device can work for more than 10 min by lighting a red bulb. Thus, this unique L-Co3O4 composite with simple fabrication method can be considered to be a promising candidate for the electrochemical energy conversion and storage.