Facile synthesis of NZMC/Co3O4 composite electrode materials at low temperature and its application in electrochemical capacitor

Abstract

A series of porous carbon/Co3O4 (NZMC–18(6)–700–3/Co3O4) composite materials with different cobalt contents were synthesized at low reaction temperature using a facile chemical precipitation method. The morphology and crystal structure of the materials were evaluated on field emission scanning electron microscope and X-ray diffraction, respectively. The results show that composite materials possess incompact lamellar structure with some irregular agglomerated Co3O4 particles adhering. The calcination temperature has a distinct influence on the morphology and electrochemical properties of porous carbon/Co3O4 composites. The electrochemical performances were measured by constant current charge/discharge tests, cyclic voltammetry, and electrochemical impedance spectroscopy tests. It is illustrated that the composite materials have outstanding charge storage ability and the specific capacitance can reach up to 462 F g−1 when the calcination temperature and cobalt content are 250 °C and 95 wt.%. With the increase of scan rate, the response current increases, and the anodic peaks and cathodic peaks shifted to higher potential and lower potential, respectively, which both illustrate that the material has excellent reversibility. The combination impedance of the electrode is only 0.674 Ω cm2 at a calcination temperature of 250 °C and is much less than those at other calcination temperatures which means that the electrode material has good conductivity.