Facile synthesis and characterizations of Bi5Nb3O15/PANI nanocomposite for supercapacitor applications

Bismuth Niobate/polyaniline (Bi₅Nb₃O₁₅(BNO))/PANI nanocomposites were synthesized and studied for use as a supercapacitor electrode. The BNO nanoparticles (NPs) were synthesized using the green route while PANI was synthesized using in-situ polymerization technique. The BNO/PANI nanocomposites were formed with different mass ratios of BNO to PANI, specifically 9:1, 8:2, and 7:3, each totaling 0.5 g for the respective combinations. The physicochemical properties of the composites were obtained using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) spectroscopy, Transmission Electron Microscopy (TEM) and UV–vis spectroscopy. The electrochemical properties were determined using cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS). The XRD pattern indicated the presence of orthorhombic BNO, and the crystalline structure of BNO remained unaffected by the inclusion of PANI. The crystalline sizes of BNO, BNO/PANI-10%, BNO/PANI-20%, and BNO/PANI-30% are 22.58 nm, 26.43 nm, 23.17 nm, and 19.07nm, respectively. Analysis using FTIR confirmed the uniform attachment of PANI on the surface of BNO nanoparticles. SEM imaging revealed a fibrous agglomerated structure in the BNO/PANI composites. TEM results showed well-dispersed nanostructures with clear lattice fringes, indicating high crystallinity. The electrochemical behavior of the BNO/PANI composite electrodes evaluated in a 1M H₂SO₄ solution showed that the BNO/PANI-30% composite electrode exhibited the highest specific capacitance of 216 Fg⁻¹ at a scan rate of 5 mV/s, surpassing the specific capacitance (10.4 Fg⁻¹) of the pristine BNO nanoparticles with more than 20 times. Additionally, the composite retains 69% of its capacitance after 5000 cycles at a current density of 2 Ag⁻¹. An asymmetric supercapacitor device (AC//BNO/PANI-30%) developed using activated carbon (AC) and BNO/PANI-30% as the negative and positive electrode respectively yielded a specific capacitance 475.44 Fg⁻¹ at a current load of 0.1 Ag⁻¹. The device retained 52.87% of its initial capacitance value after 5000 cycles, and also shows 100.14% of coulombic efficiency, indicating the potential of this composite as a promising material for supercapacitors.