(217dj) Enzymatic Synthesis of Conducting Polymer-Nanocarbon Composites For Supercapacitor-Electrode Materials

Recently, supercapacitors which can store and deliver large amounts of electrical energy in a short period of time have been highly sought after as promising energy-storage devices common to diverse energy sources. Various composites of carbon nanomaterials and conducting polymers have been actively investigated as electrode materials for supercapacitors due to their excellent electrochemical properties and physicochemical stabilities. Until now, however, harsh chemical or complex electro-deposition methods have been mainly exploited to prepare such composite materials. Oxidases including peroxidases and laccases which can catalyze the oxidation of a variety of aromatic compounds have been known to be able to catalyze the synthesis of the conducting polymers such as polyanilins, polypyrroles, polythiophenes, or their derivatives especially with the assistance of radical mediators. These enzymatic methods are environmentally benign without requiring the use of strong chemical oxidants and extreme acidic solutions. They are also very simple to perform under mild conditions in contrast to the electro-deposition methods.

In this presentation, we report the applications of the mild, simple, and environmentally-friendly enzymatic catalysis to prepare the composites of conducting polymers and various carbon nanomaterials including multiwalled carbon nanotubes, graphene oxides, and reduced graphene oxides. Polypyrrole was selected as a representative conducting polymer which was synthesized by the enzymatic catalysis of either horseradish peroxidase or laccase in the presence of hydrogen peroxide or molecular oxygen as oxidants, respectively. A radical mediator, 2,2’-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS), was used to facilitate the enzymatic synthesis of the composites with more than 60% yield. Images of the composites from scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have shown that the nancarbons are uniformly coated with polypyrrole. Various electrochemical methods were used to characterize the capacitors fabricated of the composites using cyclic voltammetry, Galvanostatic charge-discharge and electrochemical impedance spectroscopy.