Energy storage ultra porous carbon blacks by high temperature oxidation

Abstract

Ultra porous carbonaceous nanoparticles were prepared by judicious oxidation of various commercial carbon blacks (CBs) at high temperatures (1200 °C). X-ray diffraction, N₂ adsorption and microscopy analyses revealed that during such oxidation, O₂ diffuses through and reacts with CB, disordering its crystalline structure. The concurrent external and internal oxidation of CB results in tiny pores that greatly increase the specific surface area, SSA, from 240 up to 2185 ± 199 m²/g. This is about 150–200 % larger than the SSA of CB oxidized at low temperatures (450–550 °C), 50–100 % larger than the SSA of most porous CB commercially available and on par with that of commercial activated carbons (e.g. YP80). The potential of this ultra porous CB generated here for energy storage is showcased using electric double layer capacitors (EDLCs). The gravimetric capacitance of EDLCs using the above high SSA CB as active material is up to 60 % larger than those obtained from EDLCs based on YP80 or Ketjenblack at high scan rates (≥ 100 mV/s) and current densities of 0.02–5 A/g. The superior rate performance of these CBs is attributed to the high concentration of pores with a 2–8 nm radius formed largely by internal oxidation. Such pores cannot be produced at large concentrations by low temperature oxidation of CB that is used widely to enhance CB porosity. Hence, close control of the oxidation dynamics of CB can substantially increase supercapacitor performance.