Preparation and performance of Co3O4–NiO composite electrode material for supercapacitors

A Co3O4–NiO composite electrode material in water–ethanol solution was synthesized in large scale via two steps: preparation of the precursor and a calcination process. The phase structure and morphology of the prepared Co3O4–NiO composites were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Cyclic voltammetry, chronopotentiometry, and electrochemical impedance measurements were applied in a mild aqueous electrolyte (2 mol L−1 KOH) to investigate the electrochemical performance of the Co3O4–NiO composites electrode. The results indicate that the molar ratio of Ni to Co and the water–ethanol ratio had a significant influence on the electrochemical capacitive behaviors of the products. The Co3O4–NiO composite electrode shows a maximum specific capacitance of 1832 F g−1 at 2 mA cm−2 under the conditions of nCo : nNi = 1 : 1, Vwater : Valcohol = 1 : 2. In addition, the electrochemical stability was measured after 1000 continuous charge–discharge cycles at 2 mA cm−2 and only 1.863% was degraded, which shows the excellent electrochemical performance, indicating a kind of promising candidate for supercapacitors.