Anodic preparation and supercapacitive performance of nano-Co3O4/MnO2 composites

Abstract

Nano-Co₃O₄/MnO₂ composites have been prepared by anodic composite deposition from Mn(NO₃)₂ solutions containing different amounts of suspended Co₃O₄ particles. Chemical composition, crystal structure and surface morphology of the composites were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The kinetics of the formation of nano-Co₃O₄/MnO₂ composites was investigated via analyzing potential–time curves. The supercapacitive performance of the composites was examined by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). Intrinsic relations between surface structure and supercapacitive performance were discussed based on voltammetric charge analysis. When the Co₃O₄ volume fraction in the composite was 0.23, the specific capacitance of the composite reached 317 F g⁻¹ at a scan rate of 5 mV s⁻¹, increased by about 37% compared with pure MnO₂. This composite also showed enhanced power performance. Furthermore, it exhibited excellent cycling stability and the specific capacitance retention was 93.4% after 5000 charge–discharge cycles, while the retention for pure MnO₂ was 79.6%.