Effect of surface oxygen and temperature on external and micropore adsorption of water in single-walled carbon nanotubes by gravimetric and spectroscopic experiments

Pyoungchung Kim, Harry M. Meyer, Sandeep Agnihotri

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10 Scopus citations

Abstract

Gravimetric water adsorption experiments (T) 5, 20, and 35°C and 0 < P/Po < 0.95) were performed onseveral chemically and structurally distinct samples of single-walled carbon nanotubes including two activatedcarbon samples. The isotherms followed the type V curve and were fitted to a semiempirical model whichallowed the adsorptive contributions of primary sites and micropores (referred to here as pseudoexperimentalisotherms) to be distinguished with statistical confidence. The isosteric heats of water adsorption calculatedfrom experimental isotherms ranged between 46 and 58 kJ/mol. The same calculations were performed onthe separated adsorptive components (functional groups and micropore isotherms) and were found to be 0.5-16kJ/mol and 1-8.6 kJ/mol, respectively. These values are similar to those available in the current literaturereportedly estimated by calorimetric and molecular simulation techniques. From semiempirical modeling, wewere also able to qualitatively estimate temperature sensitive water specific sample properties such as theconcentration of primary sites (found directly related to % O) and the size of water clusters aggregating onprimary sites (found inversely related to % O) and those filling micropores (found directly related to thedominant pore size) and adsorption equilibrium constants. We believe that our approach is useful in interpretingexperimental water adsorption thus aiding purely simulation based methods of studying the behavior of waterin nanocarbons.

Original languageEnglish
Pages (from-to)12109-12117
Number of pages9
JournalJournal of Physical Chemistry C
Volume113
Issue number28
DOIs
StatePublished - Jul 16 2009

Funding

FundersFunder number
National Science Foundation0836365

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