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

Abstract

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 n_Co : n_Ni = 1 : 1, V_water : V_alcohol = 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.