| Autor: |
Michal Otyepka, Eva Otyepková, Lubomír Lapčík, Jiří Pechoušek, Klára Šafářová, Petr Lazar, Pavel Banáš, Radek Zbořil, Ariana Fargašová |
| Rok vydání: |
2014 |
| Předmět: |
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| Zdroj: |
Carbon. 73:448-453 |
| ISSN: |
0008-6223 |
| Popis: |
Variations in the adsorption enthalpies of acetone to few-layer graphene and graphite nanopowders were analyzed as a function of surface coverage. The adsorption enthalpies were measured by inverse gas chromatography at low monolayer coverage levels (0.1–20%). The adsorption enthalpies increased from −13 kcal/mol at the lowest coverage to −7.5 kcal/mol. We fitted the measured adsorption enthalpies as a function of coverage using a two-state model and estimated the number of high-energy sites on both materials. The graphite powder had seven times more high-energy sites than the few-layer graphene, which explains why the adsorption enthalpies for graphite increased more slowly with increasing coverage. We also performed a theoretical study based on density functional theory calculations using a functional that accounts for dispersive interactions to elucidate the nature of the high-energy adsorption sites. The calculated adsorption enthalpies ranged from −16 to −1 kcal/mol while the adsorption enthalpy to a plain graphite surface was −9 kcal/mol. The high-energy adsorption sites were localized on surface steps and edge-cavities. The adsorption enthalpies at very low coverage therefore corresponded to adsorption on steps and edge cavities, while those measured at coverage levels of ∼4% or more reflected adsorption to the flat surface. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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Full Text from ScienceDirect