Electrochimica Acta, Vol.269, 274-281, 2018
Impact of intrinsic iron on electrochemical oxidation of pencil graphite and its application as supercapacitors
Herein, we report a simple and eco-friendly method for the development of an ultra-low-cost carbon electrode for high-performance supercapacitor applications. Current work involves the electrochemical oxidation of pencil graphite electrode (PGE) to graphene oxide covered pencil graphite electrode (PGE*) by cyclic voltammetry in pH 2 acidic electrolyte (KCl-HCl). The release of intrinsic iron (Fe) from the PGE, which facilitates the electrochemical oxidation of graphite is confirmed by collective electro and physicochemical characterizations. Potential segment analysis and studies of different pencil grades suggest that electrochemical oxidation of PGE depends upon anodic potential and concentration of intrinsic Fe. Among various pencil grades (8B-6H), 6H-PGE* displays ultra-high areal capacitance (105 mF cm(-2) at 0.07 mA cm(-2)). A high concentration of intrinsic Fe in 6H-PGE facilitates the in-situ electrochemical oxidation of pencil graphite. Further, the cyclic stability over 1000 charge/discharge cycles renders excellent capacity retention of 95%, thus indicating the high rate capability of PGE* electrode. This strategy provides a novel, simple, cost-effective and eco-friendly approach for the preparation of a high-performance supercapacitor. (C) 2018 Elsevier Ltd. All rights reserved.