Tanso 232 — Abstracts

Electrochemical capacitance of carbonized polyaniline

Soshi Shiraishi, Hirokiyo Mamyouda

Department of Chemistry and Chemical Biology, Graduate School of

Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-

8515, Japan

Nitrogen-enriched carbon materials were prepared by the heat-

treatment of polyaniline (PANI). The electrochemical capacitance

of the carbonized PANI in 1.0 mol dm�3 H2SO4 electrolyte

depended on the heat-treatment. The carbonized PANI at 800 �Cshowed 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 capaci-

tance of the carbonized PANI did not correlate with the BET specific

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

layer charging as the capacitance origin for the carbonized PANI.

[TANSO 2008 (No. 232) 61–6.]

doi:10.1016/j.carbon.2008.04.003

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

Inage-ku, Chiba 263-8522, Japanb Faculty of Science, Kisarazu National College of Technology, 2-11-1

Kiyomidai-higashi, Kisarazu 292-0041, Japan

Adsorption and desorption kinetics of phenol onto activated

carbons with and without surface acidic oxygen functional groups

were examined in aqueous solutions. Aniline was also used to

compare with phenol. The surface oxygen groups was introduced

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

by out-gassing, respectively. Langmuir isotherms could be suc-

cessfully 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

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

bons, first rapid desorption and consecutive slow re-adsorption

were clearly observed for phenol and aniline, while only rapid

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

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 out-

gassed carbons simultaneously with the adsorption process.

[TANSO 2008 (No. 232) 67–71.]

doi:10.1016/j.carbon.2008.04.004

Origin of giant graphite balls produced together with carbon

nanohorns prepared by pulsed arc-discharge and a method for

their removal

Takashi Yamaguchi, Shunji Bandow, Sumio Iijima

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

Large sized spherical graphitic particles with a diameter as

large as several micrometers, so-called giant graphite balls

(GGBs), are present to some extent in samples of carbon nano-

horns (CNHs) which are prepared by the pulsed arc-discharge or

laser ablation methods. For the use of CNHs, it is necessary to

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

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

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

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

involving a combination of centrifugation and filtration is effec-

tive in removing such a small quantity of GGBs.

[TANSO 2008 (No. 232) 72–6.]

doi:10.1016/j.carbon.2008.04.005

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

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