Electrochemical capacitance of carbonized polyaniline

CARBON

4 6 ( 2 0 0 8 ) 1 1 1 0 –1 1 1 1

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Tanso 232 — Abstracts Electrochemical capacitance of carbonized polyaniline

desorption experiments from the pre-adsorbed out-gassed car-

Soshi Shiraishi, Hirokiyo Mamyouda

bons, first rapid desorption and consecutive slow re-adsorption

Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 3768515, Japan

desorption was measured from the oxidized carbons. Based on these results, for the oxidized carbons adsorption was the result of collision control kinetics between phenol and adsorption sites

Nitrogen-enriched carbon materials were prepared by the heattreatment of polyaniline (PANI). The electrochemical capacitance of the carbonized PANI in 1.0 mol dm

were clearly observed for phenol and aniline, while only rapid

3

H2SO4 electrolyte

depended on the heat-treatment. The carbonized PANI at 800 °C showed good cycle performance and 157 F g

1

of the gravimetric

capacitance. The capacitance is lower than the original PANI, but it is comparable to conventional activated carbon fibers (ACF). The specific capacitance per BET surface area for the carbonized PANI was about 40 times as much as that for the ACF. The capacitance of the carbonized PANI did not correlate with the BET specific

on the external carbon surface and meso- and macro-pores on the one hand; on the other hand not only collision control but also diffusion control kinetics was included for the out-gassed carbons. From the results of the temperature dependence of adsorption capacity and the aniline adsorption kinetics, a coupling reaction accompanied by dehydration would have taken place on the outgassed carbons simultaneously with the adsorption process. [TANSO 2008 (No. 232) 67–71.] doi:10.1016/j.carbon.2008.04.004

surface area, but strongly depended on the electronic conductivity and the nitrogen content. These results suggest the redox center of nitrogen-containing surface functionalities rather than the double

Origin of giant graphite balls produced together with carbon

layer charging as the capacitance origin for the carbonized PANI.

nanohorns prepared by pulsed arc-discharge and a method for

[TANSO 2008 (No. 232) 61–6.]

their removal Takashi Yamaguchi, Shunji Bandow, Sumio Iijima

doi:10.1016/j.carbon.2008.04.003

Division of Electrical, Electronic, Information and Materials Engineering, Graduate School of Science and Technology, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan

Influence of surface acidic functional groups on activated carbons for adsorption and desorption kinetics of phenol from aqueous solutions Koji

Moriyama a, Motoi Machida a, Masami Akikawa b, Hideki

Tatsumoto a a

(GGBs), are present to some extent in samples of carbon nanohorns (CNHs) which are prepared by the pulsed arc-discharge or laser ablation methods. For the use of CNHs, it is necessary to

Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho,

Inage-ku, Chiba 263-8522, Japan b

Large sized spherical graphitic particles with a diameter as large as several micrometers, so-called giant graphite balls

Faculty of Science, Kisarazu National College of Technology, 2-11-1

Kiyomidai-higashi, Kisarazu 292-0041, Japan

eliminate such an impurity from the sample. To decrease the GGB content, we investigated the origin of the GGBs and found a simple method for increasing the sample purity. The origin of GGBs is the exfoliated material from the carbon rod, and such an exfoliation can be nearly avoided by the preheating the carbon

Adsorption and desorption kinetics of phenol onto activated

rod to 1000 °C just prior to the arc vaporization. Using such a pre-

carbons with and without surface acidic oxygen functional groups

heat, the quantity of GGBs in the sample can be reduced from 30%

were examined in aqueous solutions. Aniline was also used to

to 0.01% (100 ppm) by weight. A simple two-stage purification

compare with phenol. The surface oxygen groups was introduced

involving a combination of centrifugation and filtration is effec-

by nitric acid oxidation after de-ashing, and completely removed

tive in removing such a small quantity of GGBs.

by out-gassing, respectively. Langmuir isotherms could be successfully employed for both activated carbons. Application of the Langmuir kinetic equation was limited to the oxidized carbons, whereas it was not a good fit for the out-gassed carbons. For

doi:10.1016/S0008-6223(08)00173-5

[TANSO 2008 (No. 232) 72–6.] doi:10.1016/j.carbon.2008.04.005