Enzymatic synthesis of polyaniline/multi-walled carbon nanotube composite with core shell structure and its electrochemical characterization for supercapacitor application

A new method involving laccase-mediator system has been developed for environmentally friendly synthesis of polyaniline/multi-walled carbon nanotubes (PANI/MWCNT) composite. Fungal laccase, potassium octocyanomolibdate (4 + ) and atmospheric oxygen served as catalyst, redox-mediator and terminal oxidant, respectively. The structure, morphology and electrical conductivity of composites with different PANI content were investigated. The energy storage of enzymatically obtained composite consists of an electrical double layer capacitance as well as pseudocapacitance of conducting polymer. The obtained PANI/MWCNT composite with PANI content ca. 49 wt.% had high specific capacitance and cycle stability during doping/dedoping. The specific capacitance of this composite measured by cyclic voltammetry technique with potential scan rate of 5 mV/s was ca. 440 F/g. The specific capacitance of the composite decreased by less than 7% of its maximum value after 1000 scan cycles between -0.1 and 0.7 V. Supercapacitor (SC) shell was made from flexible adhesive tape (regular Scotch tape) and current collector was formed after its separation from the surface of graphite foil. The ethanol dispersion of PANI/MWCNT composite was deposited on the current collector surface. The gel polymer electrolyte (polyvinyl alcohol in 1 M phosphoric acid) was employed as both electrolyte medium and separator. The energy and power densities under an operating window of 0.7 V were ca. 7.03 Wh/kg and 5.2 kW/kg, respectively.