Monodisperse Porous Carbon Nanospheres with Ultra-High Surface Area for Energy Storage in Electrochemical Capacitors

Highly porous carbon nanoparticles are very suitable materials for supercapacitor electrodes due to their combination of large surface area for ion adsorption and short pathways for fast ion diffusion. Herein we describe the synthesis of highly porous carbon nanospheres (d=90 nm) by a simple strategy that involves the preparation of monodisperse nanoparticles by the oxidative polymerization of pyrrole, followed by their direct chemical activation with KHCO3. The morphology of the nanospheres is well retained after activation, and the inorganic impurities are removed by a simple washing step with water. The porous nanospheres possess a high electrical conductivity and specific surface areas exceeding 3000 m(2) g(-1) due to their high content of micropores and small mesopores (<4 nm). Their highly developed and readily available porosity make these materials promising for use as supercapacitor electrodes. In the aqueous 1 M H2SO4 electrolyte, the porous nanospheres reach a capacitance of 262 F g(-1) and withstand an ultrahigh current density of 80 A g(-1) maintaining a capacitance above 100 F g(-1). In the organic 1 M TEABF(4)/AN and EMImTFSI/AN electrolytes, the nanoparticles reach 175 and 155 F g(-1), and the supercapacitors could be cycled up to 50 A g(-1) delivering 30 Wh kg(-1) at a power density of 20 kW kg(-1) and 31 Wh kg(-1) at a power density of 31 kW kg(-1), respectively. These results demonstrate the potential of these nanoparticles for energy storage applications.