Effect of the pore length and orientation upon the electrochemical capacitive performance of ordered mesoporous carbons

By utilizing hard template method to adjust the mesopore length, and alkali activation to generate micro pores, two hierarchical porous carbons(HPCs) were prepared. With controlling of their mesopore length and the activation conditions, the complex system composed by HPCs and electrolyte was simplified and the effect of mesopore length on the performance of HPCs as electrodes in supercapacitors was investi gated. It is found that with the mesopore length getting smaller, the ordered area gets smaller and th aggregation occurs, which is caused by the high surface energy of small grains. HPC with long pore(HPCL) exhibits a donut-like morphology with well-defined ordered mesopores and a regular orientation while in HPC with short pores(HPCS), short mesopores are only orderly distributed in small regions Longer ordered channels form unobstructed ways for ions transport in the particles while shorter chan nels, only orderly distributed in small areas, results in blocked paths, which may hinder the electrolyt ions transport. Due to the unobstructed structure, HPCL exhibits good rate capability with a capacitanc retention rate over 86% as current density increasing from 50 m A/g to 1000 m A/g. The specific capaci tance of HPCL derived from the cyclic voltammetry test at 10 m V/s is up to 201.72 F/g, while the specifi capacitance of HPCS is only 193.65 F/g.