Nitrogen-containing carbon spheres with very large uniform mesopores: The superior electrode materials for EDLC in organic electrolyte

摘要

We reported the electrochemical studies on mesoporous carbon spheres (MCS) enriched in nitrogen on frameworks serving as an electrode for electric double layer capacitor (EDLC) in an organic electrolyte. The preparation of the carbon spheres is involved in a facile polymerization-induced colloid aggregation method by using melamine-formaldehyde resin (MF) as the carbon precursor, and commercial fumed silica (Aerosi1-200) as a hard template. After the carbonization of as-formed resin-template composites at 1000 deg C under a nitrogen atmosphere, and the removal of silica template by HF treatment, monodisperse MCS with diameter size of approx 1.2 mu m, high specific surface area (up to 1460 m~2/g) and uniform pore size as large as 31 nm can be obtained. The MCS product presents a high specific capacitance as 159 F/g at 0.5 A/g. The high specific capacitance of the MCS is believed to be associated with its suitable nitrogen content that can afford pseudocapacitance as well as the high specific surface area. Furthermore, the specific capacitance of MCS can remain 130 F/g at high current density of 20 A/g. Our results show that the moderate nitrogen content can enhance the surface wettability and reduce the resistance, the large pore size can accelerate the diffusion process for the ions solvated with big organic solvent molecules in the pores. In view of the facts that precursors used in this simple process are commercially available low-cost chemicals, researches on the synthesis of such MCS materials templated by silica nanoparticles may not only be theoretically important, but also provide more options for economical and large-scale productions of mesoporous carbon materials with desired nanostructures, which might find practical applications in the fields of EDLC with high power performance.