Controlled growth of polypyrrole microtubes on disposable pencil graphite electrode and their supercapacitor behavior

In the present study, we have reported a simple, facile and robust method for the controlled growth of polypyrrole microtubes (PPy MTs) on pencil graphite electrodes (PGE) via potentiostatic deposition without using any templates or structure-directing agents. The crucial role of the supporting electrolytes in dictating the formation of microtubules is analyzed and their nucleation – growth mechanism has been studied using the well-known Scharifker - Hills and Palomer – Pardove models. These microtubules modified pencil graphite electrodes exhibit a satisfactory supercapacitor behavior which has been demonstrated using voltammetric, charge-discharge and impedance studies. It has been observed that, the tubular-like geometry of PPy is more preferable for supercapacitor behavior than other morphology of PPy in the present context. Moreover, the influences of temperature on the specific capacitance and cycle stability have also been investigated. The effect of supporting electrolytes on the supercapacitive behavior of PPy MTs modified PGE have also been analyzed and a significant enhancement in the specific capacitance value with improved rate capability is observed in acidic medium than that of neutral medium. The profound increase in the magnitude of the specific capacitance of the bare pencil graphite electrodes upon modification with PPy MTs has been ascribed to its enhanced surface roughness, fractal dimension and porosity.