Synthesis of mesoporous carbon composite and its electric double-layer formation behavior

The present study investigated that, by using an efficient thermal chemical vapor deposition technique, the mesoporous carbon composite containing carbon nanofibers (CNFs) grown on porous carbon was prepared to serve as an electrode material for electrochemical capacitors. Field-emission scanning electron microscopy and transmission electron microscopy observations showed that a large amount of CNFs with an average diameter of 8–15 nm were grown onto the porous carbon. Experiments of nitrogen adsorption reflected that the as-grown carbons have a similar surface area but different pore size distributions, compared with the original carbon. Density functional theory analysis also demonstrated that the carbon composite possessed a greater proportion of mesopores and its pore size distribution was centered at mesopore size. Electrochemical behavior of the capacitors fabricated with the carbons was investigated in two kinds of electrolytes, using 1 M KOH and 2 M Et4NBF4. Experimental results showed that compared with the original carbon, an increasing trend of capacitance for the carbon composite was found in both electrolytes. It suggested that the capacitance enhancement contributed from the growth of CNFs plays an important role not only to lower the resistance for electrolyte migration, but also to promote the pore accessibility for double-layer formation. This influence becomes more vital especially for the organic electrolyte that has a larger molecular size.