Adsorption of Organic Molecules to van der Waals Materials: Comparison of Fluorographene and Fluorographite with Graphene and Graphite.
Understanding strength and nature of noncovalent binding to surfaces imposes significant challenge both for computations and experiments. We explored the adsorption of five small nonpolar organic molecules (acetone, acetonitrile, dichloromethane, ethanol, ethyl acetate) to fluorographene and fluorographite using inverse gas chromatography and theoretical calculations, providing new insights into the strength and nature of adsorption of small organic molecules on these surfaces. The measured adsorption enthalpies on fluorographite range from -7 to -13 kcal/mol and are by 1-2 kcal/mol lower than those measured on graphene/graphite, which indicates higher affinity of organic adsorbates to fluorographene than to graphene. The dispersion-corrected functionals performed well, and the nonlocal vdW DFT functionals (particularly optB86b-vdW) achieved the best agreement with the experimental data. Computations show that the adsorption enthalpies are controlled by the interaction energy, which is dominated by London dispersion forces (∼70%). The calculations also show that bonding to structural features, like edges and steps, as well as defects does not significantly increase the adsorption enthalpies, which explains a low sensitivity of measured adsorption enthalpies to coverage. The adopted Langmuir model for fitting experimental data enabled determination of adsorption entropies. The adsorption on the fluorographene/fluorographite surface resulted in an entropy loss equal to approximately 40% of the gas phase entropy.
Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc , tř. 17. listopadu 12, 77 146 Olomouc, Czech Republic.
František
http://orcid.org/0000-0002-2623-3991
F
Karlický
Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc , tř. 17. listopadu 12, 77 146 Olomouc, Czech Republic.
Eva
E
Otyepková
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , v.v.i., Flemingovo nám. 2, 166 10 Prague 6, Czech Republic.
Rabindranath
R
Lo
Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University , Mlynská Dolina, 842 15 Bratislava, Slovakia.|Computing Center of the Slovak Academy of Sciences, Dúbravská cesta č. 9, 845 35 Bratislava, Slovakia.
Michal
M
Pitoňák
Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc , tř. 17. listopadu 12, 77 146 Olomouc, Czech Republic.
Petr
http://orcid.org/0000-0002-3741-3672
P
Jurečka
Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc , tř. 17. listopadu 12, 77 146 Olomouc, Czech Republic.
Martin
M
Pykal
Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc , tř. 17. listopadu 12, 77 146 Olomouc, Czech Republic.|Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , v.v.i., Flemingovo nám. 2, 166 10 Prague 6, Czech Republic.
Pavel
http://orcid.org/0000-0001-5292-6719
P
Hobza
Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc , tř. 17. listopadu 12, 77 146 Olomouc, Czech Republic.
Michal
http://orcid.org/0000-0002-1066-5677
M
Otyepka