Supercritical Hydrogen Adsorption of Ultramicropore-Enriched Single-Wall Carbon Nanotube Sheet

J. Phys. Chem. C, 111 (46), 17448 -17450, 2007. 10.1021/jp0772023 S1932-7447(07)07202-0
Web Release Date: October 25, 2007

Supercritical Hydrogen Adsorption of Ultramicropore-Enriched Single-Wall Carbon Nanotube Sheet

Dong Young Kim, Cheol-Min Yang, Masahiro Yamamoto, Dae Ho Lee, Yoshiyuki Hattori, Kunimitsu Takahashi, Hirofumi Kanoh, and Katsumi Kaneko*

Graduate School of Science, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda 386-8567, Japan, and Institute of Research and Innovation, Laser Research Center, 1201 Takada, Kashiwa, Chiba, 277-0861, Japan

Received: September 7, 2007

Abstract:

Ultramicropore-enriched single-wall carbon nanotube (SWCNT) sheet was prepared by a filtration process after acid treatment using HNO₃/H₂SO₄ solution. Field emission scanning electron microscopic observation showed that a highly dense entangled structure of SWCNT bundles was formed by acid treatment. The pore structure of the SWCNT sheet was evaluated from adsorption isotherms of N₂ at 77 K and CO₂ at 273 K. The SWCNT sheet gave remarkably developed uniform ultramicroporosity and reduced mesoporosity through formation of the highly packed sheet. The acid treatment remarkably increased the adsorption amount of supercritical hydrogen at 77 K by about three times. The enhancement of hydrogen adsorption by acid treatment came mainly from the increase in the ultramicropores because the increase in isosteric heat of hydrogen adsorption by acid treatment was only 0.1-0.2 kJ mol^-1.

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