Supercapacitors with Prussian Blue Derived Carbon Encapsulated Fe/Fe3C Nanocomposites

Abstract

A one-step synthesis of carbon encapsulated Fe/Fe3C nanoparticles by pyrolyzing single source precursor of Prussian Blue (Iron (III) ferrocyanide) for its usage as anode material in high-performance supercapacitors is reported. The synthetic method produces 3D doughnut shaped porous structures comprising numerous interconnected Fe/Fe3C nanoparticles entirely encapsulated within layers of graphitic carbon. Such a porous structure facilitates electrolytic ion diffusion during charge storage on Fe/Fe3C nanoparticles through surface or near surface- based faradaic reactions, while the metallic iron helps enhancing the electronic conductivity of the electroactive material. Accordingly, the charge storage in such carbon encapsulated Fe/Fe3C nanoparticles is governed by capacitive as well as diffusion-controlled processes at lower scan rates, and is taken over by capacitive processes at higher scan rates. The material achieves a specific capacitance of 223 F g−1 at a scan rate of 10 mV s−1 along with compelling cycling performance exhibiting a little decay in capacitance over 20,000 cycles. When coupled with activated-carbon cathode, Fe/Fe3C//activated-carbon asymmetric supercapacitor out-performs many recently reported supercapacitors.