Electropolymerization of polyaniline on coated activated carbon derived from human hair as a bilayer electrode for supercapacitor applications

Abstract

In this study, electropolymerization was used to deposit polyaniline (PANI) layer on the surface of coated activated carbon derived from human hair (HH-AC) using nickel foam as conducting substrate via cyclic voltammetry (CV) at different cycle numbers. The bilayer HH-AC/PANI electrode was prepared in a non-acidic medium unlike other conventional electrochemical polymerization methods, and characterized using Raman spectroscopy, UV–visible spectroscopy, scanning electron microscope (SEM), and nitrogen physisorption measurements to determine the chemical composition, electronic structure, surface morphology, and textural properties, respectively. The results showed that a PANI layer was successfully deposited on the surface of HH-AC. The electrochemical evaluation was carried out using CV, galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques in 2.5 M KNO3 neutral electrolyte. The optimal bilayer electrode prepared by 8-cycles and denoted as HH-AC/PANI-8 shows an excellent specific capacitance of 220 F g−1 at a positive potential, which is almost twice of 121 F g−1 for that of pristine HH-AC operated in a three-electrode system. Furthermore, for practical application, a symmetric device comprising HH-AC/PANI-8 bilayer electrode was assembled and tested in a two-electrode system configuration, leading to a specific energy of 28.6 W h kg−1 and a specific power of 800W kg−1, at a specific current of 1 A g−1 and voltage window of 1.6 V. Besides, the capacitance retention of the device remained 83 % after 10,000 cycles at 5 A g−1, indicating a long lifespan. These results suggest that the HH-AC/PANI-8 bilayer electrode is a promising candidate for high-performance supercapacitors.