Carbon slit pore model incorporating surface energetical heterogeneity and geometrical corrugation
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Carbon slit pore model incorporating surface energetical heterogeneity and geometrical corrugation Jacek Jagiello • James P. Olivier
Received: 17 January 2013 / Accepted: 15 February 2013 / Published online: 1 March 2013 Ó Springer Science+Business Media New York 2013
Abstract In our recent paper (Jagiello and Olivier, Carbon 55:70–80, 2013) we considered introducing energetical heterogeneity (EH) and geometrical corrugation (GC) to the pore walls of the standard carbon slit pore model. We treated these two effects independently and we found that each of them provides significant improvement to the carbon model. The present work is a continuation of the previous one, as we include both effects in one comprehensive model. The existing standard slit pore model widely used for the characterization of activated carbons assumes graphite-like energetically uniform pore walls. As a result of this assumption adsorption isotherms calculated by the non-local density functional theory (NLDFT) do not fit accurately the experimental N2 data measured for real activated carbons. Assuming a graphene-based structure for activated carbons and using a two-dimensional-NLDFT treatment of the fluid density in the pores we present energetically heterogeneous and geometrically corrugated (EH–GC) surface model for carbon pores. Some parameters of the model were obtained by fitting the model to the reference adsorption data for non-graphitized carbon black. For testing, we applied the new model to the pore size analysis of porous carbons that had given poor results when analyzed using the standard slit pore model. We obtained an excellent fit of the new model to the experimental data and we found that the typical artifacts of the standard model were eliminated.
J. Jagiello (&) J. P. Olivier Micromeritics Instrument Corporation, 4356 Communications Drive, Norcross, GA 30093, USA e-mail: [email protected]
Keywords Characterization of porous carbons Pore size distribution Non-local density functional theory Modification of the standard carbon slit pore model
1 Introduction In the first application (Seaton et al. 1989) of a molecular model for the characterization of the pore size distribution (PSD) of activated carbons, the carbon pores were modeled as slits between infinitely extended graphitic walls. Due to its simplicity, the slit pore model has become the standard in the development of methods for the characterization of carbon PSD. The solid–fluid interaction potential in this model was described by the closed form formula (Steele 1973). Various approaches for calculating densities of fluids adsorbed in such pores have been employed. Application of molecular models was initiated using density functional theory (DFT) in its local version (Evans and Tarazona 1984) this approach was then refined by using more advanced fluid theories such as non-local DFT (NLDFT) (Tarazona 1985, 1987; Lastoskie et al. 1993; Olivier et al. 1994) and the fundamental measure theory (Rosenfeld 1989) as well as grand canonical Monte Carlo
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