Electrochemical Synthesis and Characterisation of Polyaniline-Based Nanocomposites for Supercapacitor Applications

The development of high-performance energy storage materials from inexpensive and accessible precursors is a strategic research priority for Nigeria's transition toward renewable energy technologies. Polyaniline-based nanocomposites have attracted considerable attention as supercapacitor electrode materials due to their high theoretical capacitance, easy synthesis, and low material cost. This study synthesised polyaniline and polyaniline-graphene oxide nanocomposites by electrochemical polymerisation on graphite substrates and evaluated their structural, morphological, and electrochemical properties for supercapacitor applications. Synthesis conditions including applied potential, monomer concentration, acid electrolyte type and concentration, and polymerisation time were systematically optimised. Composites were characterised by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and ultraviolet-visible spectroscopy. Electrochemical performance was evaluated by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy in a three-electrode cell using sulphuric acid electrolyte. Neat polyaniline showed a specific capacitance of 310 F/g at 1 A/g current density. Incorporation of graphene oxide at 10 weight percent improved the specific capacitance to 524 F/g, attributed to increased electrode surface area and synergistic charge storage contributions. Capacitance retention was 88 percent after 1,000 charge-discharge cycles, indicating acceptable electrochemical stability. Energy density was calculated as 18.7 Wh/kg. The enhanced performance of the nanocomposite is attributed to the dual electrochemical double-layer and pseudocapacitive charge storage mechanisms confirmed by the impedance analysis. These results contribute to the development of locally manufacturable energy storage components for off-grid solar energy systems in Nigeria.

Keywords: polyaniline, graphene oxide, supercapacitor, electrochemical synthesis, energy storage