Bio-polymer pectin as morphological modifier for polyaniline: Stability enhancement for energy storage applications

Bio-polymer pectin has been employed as a morphological modifier and doping agent to develop materials with improved specific properties and functions of polyaniline. Polyaniline (PANi) is an interesting electrode material for electrochemical energy storage due to its inexpensive cost, easy manufacturing, electroactivity, redox characteristics, and suitable capacitance with a major drawback of poor cyclic stability performance. Performance-enhanced polyaniline was synthesized by a simple chemical oxidative method at 5 °C using inexpensive and nontoxic pectin as a stabilizer. For a comparative study process, bare PANi was also synthesized without pectin. As-synthesized bare PANi(B_PANi) and pectin-modified PANi(M_PANi) were analysed by various techniques to understand the chemical bonding nature and interaction between pectin and PANi. Field emission scanning electron microscopy (FESEM) analysis demonstrated the spherical ball-like morphology of M_PANi generated by collective PANi nanorods with high interfacial contact. X-ray photoelectron spectroscopy (XPS) analysis proves the interfacial interaction between pectin and PANi nanorods. Symmetric supercapacitor device fabricated with M_PANi as electrode material with biocompatible KCl gel electrolyte exhibited a maximum of 103.4 mF cm⁻² specific capacitance at a current density of 3 mA cm⁻². The cyclic stability of the device was found to be 58 % over 5000 cycles, whereas B_PANi exhibited only 24.8 % over 2500 cycles. The electrode compatibility was also subsequently examined using an acid-based gel electrolyte, which yielded a substantially superior cyclic stability of 81 % over 5000 cycles. Because of its low cost and ability to attain over 98 % coulombic efficiency with improved cycle stability, M_PANi is an attractive electrode material for next-generation biocompatible low-cost solid-state energy storage applications.