Porous carbon nanospheres derived from chlorination of bis(cyclopentadienyl)titanium dichloride and their electrochemical capacitor performance

Conglomerated and accreted porous carbon spheres have been obtained by the chlorination reaction of bis(cyclopentadienyl)titanium dichloride as carbon precursor. The spheres size distribution, derived from scanning electron microscopy observations, shows that the diameter intervals decreases from 70–525 nm at 400 °C to 40–370 nm at 900 °C. High-resolution transmission electron microscopy observations indicate that the spheres are formed by open and curved randomly stacked graphene-like layers. Electron energy loss spectroscopy studies show relative sp2/sp3 ratio higher than 95% and mass-density values (1.1–1.6 g cm−3) smaller than graphite. Nitrogen adsorption measurements reveal the presence of micro and mesopores whose contributions to the total porosity greatly depend on the preparation temperature. Galvanostatic charging–discharging measurements on the carbon material synthesized at 900 °C provide a specific capacitance of 106 F g−1 in the aqueous H2SO4 electrolyte and 80 F g−1 in the aprotic (C2H5)4NBF4/acetonitrile medium. These high values suggest the potentiality of this material for electrical energy storage in electrochemical double layer capacitors.