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Molecular Modeling and Adsorption Properties of Ordered Silica-Templated CMK Mesoporous Carbons
journal contribution
posted on 2017-02-06, 00:00 authored by Surendra
Kumar Jain, Roland J.-M. Pellenq, Keith E. Gubbins, Xuan PengRealistic molecular
models of silica-templated CMK-1, CMK-3, and
CMK-5 carbon materials have been developed by using carbon rods and
carbon pipes that were obtained by adsorbing carbon in a model MCM-41
pore. The interactions between the carbon atoms with the silica matrix
were described using the PN-Traz potential, and the interaction between
the carbon atoms was calculated by the reactive empirical bond order
(REBO) potential. Carbon rods and pipes with different thicknesses
were obtained by changing the silica–carbon interaction strength,
the temperature, and the chemical potential of carbon vapor adsorption.
These equilibrium structures were further used to obtain the atomic
models of CMK-1, CMK-3, and CMK-5 materials using the same symmetry
as found in TEM pictures. These models are further refined and made
more realistic by adding interconnections between the carbon rods
and carbon pipes. We calculated the geometric pore size distribution
of the different models of CMK-5 and found that the presence of interconnections
results in some new features in the pore size distribution. Argon
adsorption properties were investigated using GCMC simulations to
characterize these materials at 77 K. We found that the presence of
interconnection results greatly improves the agreement with available
experimental data by shifting the capillary condensation to lower
pressures. Adding interconnections also induces smoother adsorption/condensation
isotherms, and desorption/evaporation curves show a sharp jump. These
features reflex the complexity of the nanovoids in CMKs in terms of
their pore morphology and topology.