(355i) Influence of Dopants on the Electrochemical Properties of Conducting Polymers As Electrodes for Supercapacitors

Conducting polymers are class of functional polymers having conjugated chain structures. Among them, polyaniline (PAni) and polypyrrole (PPy) are well known for their excellent electrochemical properties as electrode materials of supercapacitors. To achieve high conductivity in conducting polymers, doping is necessary. In conducting polymers, dopants tend to be randomly distributed within the conjugated polymer affecting the structural and electrical properties of conducting polymers and as a result the electrochemical performance are strongly affected by the resulting structural and electronic disorder.

In this paper, the influence of dopants: hydrochloric acid (HCl), perchloric acid (PrA), sulfuric acid (SA), p-toluene sulfonic acid (p-TSA), phosphoric acid (PhAc) and phytic acid (PA), on electrochemical performance of PAni and PPy were evaluated, respectively. For better comparation and understanding of the effect of dopants on the electrochemical properties of conducting polymers, the morphologies and structures of PAni and PPy obtained by using different dopants were characterized by SEM, TEM, XRD, TGA, etc. Their electrochemical performance as electrode materials for supercapacitors were evaluated by using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS). Results showed that, for both PAni and PPy, a smaller size of dopants helps to form a more compact coating with better conductivity in which ions could easily diffuse in and out of the conducting polymers. Thus, better electrochemical performance and higher capacitance could be obtained. However, during charge-discharge process the conducting polymers with smaller dopants were much easier to swell and shrink that makes their degradation faster. On the other hand, bigger size dopants showed better stability at higher scan rates and current densities. This work demonstrated that the size of dopants played a big role on the electrochemical performance and stability of conducting polymers when they were used as supercapacitor electrodes.