A three-dimensional nanostructured PANI/MnO _x porous microsphere and its capacitive performance

Three-dimensional nanostructured polyaniline (PANI) and manganese oxide (MnO _x ) composite porous microspheres were prepared by oxidizing aniline with KMnO₄ under interfacial chemical synthesis with 4-amino-thiophenol (4-ATP) as the structure-directing agent on the Au substrate. Surface morphology and chemical composition of PANI/MnO _x microsphere were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, thermo gravimetric-differential thermal analysis, and Fourier transform infrared spectrum. The result displayed that concentration of KMnO₄ played a key role in forming the 3D nanostructured porous microspheres. To obtain the regular shapes and uniform sizes of the porous microspheres, the optimal concentration of oxidant was 0.15 mol L⁻¹. The electrochemistry performances of PANI/MnO _x microsphere were determined by cyclic voltammograms, electrochemical impedance spectroscopy, and galvanostatic charge–discharge. The specific capacitance of the 3D nanostructured PANI–MnO _x porous microspheres exhibited a maximum value of 828 F g⁻¹ at current density of 2 mA cm⁻² over a potential range of 0.0–0.9 V versus SCE. It has improved 365 and 88 % comparing with that of PANI (178 F g⁻¹) and MnO _x (440 F g⁻¹) obtained at the similar condition. The charge–discharge tests showed the PANI/MnO _x microsphere possessed a good cycling stability. It maintained about 84.2 % of the initial capacitance after 1000 cycles at a current density of 2.0 mA cm⁻².