Comparative synergistic effect of hybrid composites based polyaniline wrapped metallic oxides (Ni, Fe and Mn) and its capacitive performance as electrodes for supercapacitor

Regarding the demand for new technologies for energy storage devices, supercapacitors can bridge the gap between conventional capacitors and batteries in terms of energy and power densities. It is reported that metal oxides (MOs), such as oxides of iron (Fe2O3), nickel (NiO), and manganese (MnO2, Mn2O3), among others, can act as a nucleus to obtain composites, interconnecting the polymer chains, with dimensions ranging from micrometer to nanometers, in addition to producing a porous morphology, which would be able to reach high specific surface areas. In this study, polyaniline (PANI) and its respective composites with iron oxides (Fe2O3) (PANI/Fe2O3), oxides nickel (NiO) (PANI/NiO) and manganese (MnO2, Mn2O3) (PANI/MnxOy) are developed, characterized, and compared. The field emission gun-scanning electron microscopy (FEG-SEM) images display that composites present porous morphology and dimensions ranging from micrometer, which can reach high specific surface areas. The Raman data exhibits that characteristic bands of polyaniline present in the composite materials underwent significant changes, which can be attributed to interactions of imine groups with metallic oxides. These interactions can be of the electrostatic, metal-organic, or hydrogen bonding type and directly influence the charge transfer and conductivity process, thus contributing to the increase in electrochemical performance. By electrochemical analyses, the nanocomposite materials synergism is proved, especially for PANI/MnxOy. By electrochemical impedance spectroscopy (EIS), capacitive profiles of synthesized materials are clear with a phase angle close to 90° in lower frequencies regions associated with smaller impedance modulus values in the whole analyzed frequency range. PANI/MnxOy composite also shows the highest capacitance value evaluated from a galvanostatic charge and discharge (GCD) of 115.78 F g−1. This is reinforced by its higher specific capacitance, energy, and power values of 205.55 F g−1, 21.9 W kg−1, and 1850 Wh kg−1, respectively, per CV.