Effects of Graphene Layer Size on the Adsorption of Fluids on Graphitized Thermal Carbon Black. A Computer Simulation Study

Abstract

ABSTRACT:The adsorption of Lennard-Jones fluids (argon and nitrogen) onto a graphitized thermal carbon black surface was studied with a Grand Canonical Monte Carlo Simulation (GCMC). The surface was assumed to be finite in length and composed of three graphene layers. When the GCMC simulation was used to describe adsorption on a graphite surface, an over-prediction of the isotherm was consistently observed in the pressure regions where the first and second layers are formed. To remove this over-prediction, surface mediation was accounted for to reduce the fluid-fluid interaction.Do and co-workers have introduced the so-called surface-mediation damping factor to correct the over-prediction for the case of a graphite surface of infinite extent, and this approach has yielded a good description of the adsorption isotherm. In this paper, the effects of the finite size of the graphene layer on the adsorption isotherm and how these would affect the extent of the surface mediation were studied. It was found that this finite-surface model provides a better description of the experimental data for graphitized thermal carbon black of high surface area (i.e. small crystallite size) while the infinite-surface model describes data for carbon black of very low surface area (i.e. large crystallite size).

Explanation of the unusual peak of calorimetric heat in the adsorption of nitrogen, argon and methane on graphitized thermal carbon black

“…In this study all graphite layers are rectangular with a linear dimension in x and y of 92.3 and 98.4 A ˚, respectively. This is due to the fact that our recent study of the effects of the length of finite surface on the simulation results 16 shows good agreement between the simulation results for graphene layer lengths of 100 and 150 A ˚and the experimental data of argon on graphitized thermal carbon black at 87.3 K taken from Olivier. 25 Although at the pressure region between 150 and 1000 Pa at which the formation of the monolayer occurs, the simulated isotherm for the graphene layer length 100 A ˚is less than the data, the result agrees very well with the data when the monolayer is nearly completed (surface coverage (y) = 1) as shown in Fig.…”

“…Using the fluctuation theory, the isosteric heat 25 and the modified GCMC results for various lengths of the graphene layer of the finite surface. 16 This journal is c the Owner Societies 2008 Phys. Chem.…”

“…1,2,[7][8][9] As a response to these experimental works, adsorption of argon and nitrogen on carbon surfaces has been theoretically studied by using a Density Functional Theory (DFT) simulation 10 and a Grand Canonical Monte Carlo (GCMC) simulation, [11][12][13][14][15] and the simulated isotherms agree well with the experimental data. We have recently presented adsorption isotherms of these adsorbates on a finite surface of either the perfectly graphitized 16 or the defective carbon surfaces. 15 The use of finite surface is because real carbon surfaces are neither infinite nor uniform, but rather they are finite in size 17 and they contain functional groups and morphological defects on the basal graphene layers.…”

Effects of surface mediation on the adsorption isotherm and heat of adsorption of argon on graphitized thermal carbon black

“…The adsorption of argon on GTCB is one of the simplest systems to study and it has received considerable experimental and theoretical attention [2][3][4][5][6][7][8][9]. Despite numerous simulation studies in the literature, the commonly used models do not account for the nonadditivity between the fluid-fluid interaction and the solidfluid interaction and therefore fail to reproduce accurately the experimental data.…”