Studies On Preparation And Electrochemical Behaviors Of Novel Porous Carbon Materials For Supercapacitor

Electrochemical capacitors (ECs), named supercapacitors or psuedocapacitors,have possessed a significant amount of interest and attention because of their variousadvantages, such as high energy and power density, long-time cycle life and low cost.It is well known that the key component of the ECs is the electrode material, whichdetermines it’s performance. Therefore, the synthesis and optimization of electrodematerials have been the emphasis in both academic and industrial field. Currently, themost important electrode materials for ECs are the porous carbon materials. In orderto prepare the novel porous carbon materials for ECs, the polyaniline/activatedmesocarbon microbeads (PANI/ACMB) composites are prepared by in situ chemicaloxidation polymerization. Besides, with the direct carbonization using PANI/ACMBcomposites as the precursor and subsequent activated with16M HNO3, the activatednitrogen-enriched novel carbons (NENCs) can be obtained. Furthermore, through thenanocasting method, the ordered mesoporous/microporous carbon materials areprepared. The physicl and electrochemical behaviors of the materials are investigated.The PANI/ACMB composites are prepared by in situ chemical oxidationpolymerization. It can be found that PANI has been uniformly deposited on thesurface of the ACMB to form the leechee-like morphology. The results of theelectrochemical measurements indicate that the PANI/ACMB composites havepossessed better electrochemical performance than that of the pure ACMB. And thecyclic voltammograms show that PANI/ACMB composites have the maximumspecific capacitance of433.8F g-1. Moreover, the electrochemical performance of thecoin supercapacitor represents both high specific capacitance and excellent cyclestability, the specific capacitance of the PANI/ACMB supercapacitor is much higherthan the pure ACMB supercapacitor even after500cycles.In order to improve the cycle stability of the PANI/ACMB composites, withdirect carbonization using PANI/ACMB composites as the precusor and subsequentactivated with16M HNO3, the activated nitrogen-enriched novel carbons (NENCs) can be obtained. Herein, the influences of the carbonization temperatures on thestructure and morphology of the NENCs samples are investigated. The results showthat the physical and electrochemical properties of the NENCs are greatly affected bythe carbonization process conditions. The electrochemical tests demonstrate that theNENCs samples carbonized at600℃show the highest specific capacitance of385.0F g-1at the current density of1A g-1. Furthermore, the capacity retention of theNENCs-600supercapacitor is as high as92.8%over2500cycles.The NENCs carbonized at600℃and activated by16M HNO3are used as theelectrode material for supercapacitor. The supercapacitive behaviors of the NENCssupercapacitors with0.5M K2SO4,1M H2SO4and6M KOH aqueous electrolytesare investigated. The results show that all the NENCs supercapacitors performdefinitely supercapacitive behaviors in6M KOH electrolyte, representing muchbetter electrochemical performance with more excellent reversibility, shorterrelaxation time of1.11s and nearly ideal polarizability. The specific capacitance ofthe supercapacitors using NENCs as the active electrode material is89.5F g-1.To improve the electrolyte ion transport rate and energy density of CDC, a seriesof ordered mesoporous/microporous carbon materials derived from chromiumcarbide-derived carbons (CDCs) are prepared. It has been found that the CDCs-2(thecontent of chromium in the precursor of chromium carbide-derived carbons is35%)exhibits the chain-like morphology with high surface area (1236m2g-1), large porevolume (0.76cm3g-1), and the good mesopore size centered at3.43nm. And theresults of the electrochemical measurements display that the sample CDCs-2exhibitsa high capacitance of242.7F g-1at1A g-1and good cycling stability with coulombicefficiency of100%over10000cycles.