Electrochemical synthesis of porous polyaniline for supercapacitor application

Abstract Polyaniline (PANI) is a promising material for energy storage technologies such as supercapacitors due to its unique properties such as high conductivity, redox activity, excellent environmental stability, low cost, and easy preparation. However, enhancing the charge storage capability of PANI and improving the capacitance of PANI is a challenge. To address this challenge, a novel and facile electrochemical approach to synthesizing the porous PANI is proposed. This approach varies from conventional methods by eliminating the necessity for templates to form pores in the PANI matrix. Pore formation was facilitated using the readily available organic dye, methylene blue (MB). Electrochemical polymerization of PANI was carried out using cyclic voltammetry (CV) within the potential range of 0 V–1.4 V in a 0.1 M H 2 SO 4 electrolyte containing 0.025 M MB. Characteristic redox peaks at approximately 0.5 V, 0.9 V, and 0.2 V confirmed the successful synthesis of PANI. The polymer was electrodeposited onto a stainless-steel (SS) substrate pre-adsorbed with MB and subsequently immersed in ethanol to extract the dye. Porous structures significantly enhance the surface area of the PANI matrix, facilitating rapid ion diffusion and improving charge storage capability. Synthesized material was structurally characterized by the Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and X-ray diffraction (XRD). FTIR analysis confirmed the deposition of PANI on the electrode substrate. SEM images showed pore structures in the PANI matrix. EDX data showed the presence of elements N and C, confirming the deposition of PANI. The electrochemical characterization of the material was carried out using CV, electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge (GCD) technique in 0.5 M H 2 SO 4 electrolyte using a three-electrode configuration to illustrate the electrochemical performance of the material. The CV data showed a significant enhancement in the capacitance of porous PANI to 13 mF cm −2 at the 5 mV/s scan rate compared to the capacitance of PANI of 7.6 mF cm −2 . The capacitive and diffusive contributions quantified using Dunn’s method were 24.8 % and 75.2 % respectively. GCD data showed an energy density of 2.056 μ Wh cm −2 at the power density of 0.034 mW cm −2 and a capacitance retention of 98 % after the 10 cycles. EIS data showed the enhancement of electrochemical performances with less charge transfer resistance for porous PANI. These results concluded the efficacy of the proposed electrochemical synthesis method in enhancing the charge storage capability of PANI for its potential for high-performance supercapacitor applications.