Characterization of polyanilines synthesized at different pH for electrochemical sensing and supercapacitor applications

Abstract

Here we synthesized different polyanilines from the aqueous HCl solutions of different pH through chemical oxidative polymerization of aniline using potassium persulphate as oxidant at 10 ± 2 °C. The polymers were characterized using UV–Visible spectra, FT-IR and SEM. The dependence of pH of the acid medium used for the synthesis on the electrochemical characteristics - specific capacitance and current sensing of the synthesized polyanilines were studied by cyclic voltammetric and chronopotentiometric techniques. Polyaniline experiences a sharp drop in its performance as a supercapacitor when it is synthesized from a higher pH medium. The highest specific capacitance was obtained for polyaniline synthesized from pH = 0 medium. We have also verified that the electrochemical reactions of all the synthesized polyanilines can sense their electrical working energetic conditions. The sensing capabilities (here the current sensing) of polyanilines synthesized at different pH showed a linear relationship between the consumed electrical energy and the applied current. The current sensitivity of polyaniline slightly decreases as the pH of reaction media increases from 0 to 2 and markedly decreases for polyaniline from solutions of pH above 2.