Effect of doping ions on the electrochemical capacitance properties of pristine polypyrrole

• 1、School of Electronic and Information Engineering, Xi’an Jiaotong University
• 2、School of Electronic and Information Engineering- Xi’an Jiaotong University

Abstract：Conducting polypyrrole films (PPy) doped by p-toluenesulfonate (TOS-), ClO4- and Cl- were electrochemically prepared, respectively. The electrochemical capacitance properties of the PPy films were investigated with cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques. The morphology observation and structure analysis of PPy films were performed on Scanning Electron Microscope (SEM) and X-ray diffraction (XRD). The results show that PPy-Cl and PPy-TOS were characterized with highly porous and ordering structure, which leads to their very fast ion switch processes. Moreover, they exhibit a rectangle-like shape of voltammetry characteristics even at scanning rate 50mV/s, a linear variation of the voltage with respect to time in charge-discharge process and almost ideal capacitance behavior in low frequency even on deeply charged/discharged states in 1M KCl solution. Furthermore, specific capacitance of PPy-Cl would reach 270F/g (scanning rate 5mV/s) or 175F/g (scanning rate 200mV/s). In addition, with heaver doping ion (TOS-), PPy-TOS was characterized with a little lower specific capacitance (146F/g, scanning rate 5mv/s) but very rapidly charge/discharge ability (specific capacitance 123.6F/g at scanning rate 200mV/s).All of the above imply that the PPy-Cl and PPy-TOS were two kinds of ideal electrode material of supercapacitor.

Keywords： Polypyrrole, Capacitance, Electrochemical polymerization, EIS, SEM, XRD