Electrochemical performance of rod-type ordered mesoporous carbons with different rod lengths for electric double-layer capacitors

Rod-type ordered mesoporous carbons were synthesized by the direct carbonization of sulfuric-acid-treated silica/triblock copolymer composites, followed by etching the silica with a HF solution. The morphologies, microstructures and pore structures of the mesoporous carbons were investigated by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and nitrogen sorption. Their electrochemical performance as electrodes for supercapacitors was investigated by impedance spectroscopy and charge/discharge tests. It was found that the rod length of the mesoporous carbons can be changed from one to tens of micrometers by changing the synthesis parameters. The sample with the longest rod length has the highest specific capacitance. The sample with two pore sizes has the highest capacitance retention ratio of 92% at a high current density of 2 A/g.