A critical review of adsorption methods that are currently used in the characterization of ordered organic−inorganic nanocomposite materials is presented, and the adsorption methodology that is potentially useful for this characterization, but has not yet been applied, is discussed. The ordered organic−inorganic nanocomposites include surface-functionalized ordered mesoporous materials (OMMs) with siliceous frameworks (synthesized either via postsynthesis surface modification or via direct co-condensation method), periodic mesoporous organosilicas, and surfactant-containing OMMs. This review covers the methods for determination of the specific surface area and pore volume. The available methods for mesopore size analysis are critically compared and evaluated, with special emphasis on the recent developments related to the application of advanced computational methods for studying adsorption in porous media and to the direct modeling of adsorption using highly ordered surface-functionalized OMMs as model a...

Gas adsorption characterization of ordered organic-inorganic nanocomposite materials

Electrical energy storage (EES) is one of the most critical areas of technological research around the world. Storing and efficiently using electricity generated by intermittent sources and the transition of our transportation fleet to electric drive depend fundamentally on the development of EES systems with high energy and power densities. Supercapacitors are promising devices for highly efficient energy storage and power management, yet they still suffer from moderate energy densities compared to batteries. To establish a detailed understanding of the science and technology of carbon/carbon supercapacitors, this review discusses the basic principles of the electrical double-layer (EDL), especially regarding the correlation between ion size/ion solvation and the pore size of porous carbon electrodes. We summarize the key aspects of various carbon materials synthesized for use in supercapacitors. With the objective of improving the energy density, the last two sections are dedicated to strategies to increase the capacitance by either introducing pseudocapacitive materials or by using novel electrolytes that allow to increasing the cell voltage. In particular, advances in ionic liquids, but also in the field of organic electrolytes, are discussed and electrode mass balancing is expanded because of its importance to create higher performance asymmetric electrochemical capacitors.

Carbons and Electrolytes for Advanced Supercapacitors

http://fcbt.mse.gatech.edu/PDF/Bersra2007.pdf

A review on fundamentals and applications of electrophoretic deposition (EPD)

Pore size determination in modified micro- and mesoporous materials. Pitfalls and limitations in gas adsorption data analysis

Supercapacitors are electrochemical energy storage devices that operate on the simple mechanism of adsorption of ions from an electrolyte on a high-surface-area electrode. Over the past decade, the performance of supercapacitors has greatly improved, as electrode materials have been tuned at the nanoscale and electrolytes have gained an active role, enabling more efficient storage mechanisms. In porous carbon materials with subnanometre pores, the desolvation of the ions leads to surprisingly high capacitances. Oxide materials store charge by surface redox reactions, leading to the pseudocapacitive effect. Understanding the physical mechanisms underlying charge storage in these materials is important for further development of supercapacitors. Here we review recent progress, from both in situ experiments and advanced simulation techniques, in understanding the charge storage mechanism in carbon- and oxide-based supercapacitors. We also discuss the challenges that still need to be addressed for building better supercapacitors.

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Efficient storage mechanisms for building better supercapacitors

Gas adsorption is an important tool for the characterisation of porous solids and fine powders. Major advances in recent years have made it necessary to update the 1985 IUPAC manual on Reporting Physisorption Data for Gas/Solid Systems. The aims of the present document are to clarify and standardise the presentation, nomenclature and methodology associated with the application of physisorption for surface area assessment and pore size analysis and to draw attention to remaining problems in the interpretation of physisorption data.

Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report)

The nitrogen adsorption isotherm measured at 77 K in the relative pressure range from about 5 × 10-7 to 0.988 for a macroporous silica is reported in a tabular form. The isotherm data are in good agreement in the high-pressure range with the reference data published by Gregg and Sing and by Kiselev and Aristov and provide an extension of the latter data to the low-pressure region, for which a reliable reference isotherm was not availalable in the literature. Application of the currently reported reference adsorption isotherm is discussed. The data can be used in comparative analysis (αs-plot or t-plot) to evaluate the external surface area, micropore volume, primary mesopore volume, and total surface area as well as to analyze surface properties of silica-based materials. The adsorption isotherm can also be applied as a statistical film thickness curve in the calculation of the mesopore size distribution.

Standard Nitrogen Adsorption Data for Characterization of Nanoporous Silicas

2D-NLDFT adsorption models for carbon slit-shaped pores with surface energetical heterogeneity and geometrical corrugation

The formalism of (nonlocal) density functional theory provides an attractive way to describe the physical adsorption process at the fluid-solid interface. It provides numerical results of analytic precision in a small fraction of the time required by a simulation technique. In particular, the ability to model adsorption in a pore space of slit-like or cylindrical geometry has led to useful methods for extracting pore size distribution information from experimental adsorption isotherms. However, critical comparisons of experimental isotherms with the isotherms predicted by density functional theory have shown important differences when using the usual prescription for the nonlocal free energy density functional. It is clear that these differences would affect the accuracy of such pore size information. We show in this paper how a small modification to the mean field computation of the intermolecular attractive potential results in excellent agreement with experiment for the systems studied.

Modeling Physical Adsorption on Porous and Nonporous Solids Using Density Functional Theory

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.

James P. Olivier

Papers

Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report)

Standard Nitrogen Adsorption Data for Characterization of Nanoporous Silicas

2D-NLDFT adsorption models for carbon slit-shaped pores with surface energetical heterogeneity and geometrical corrugation

Modeling Physical Adsorption on Porous and Nonporous Solids Using Density Functional Theory

Carbon slit pore model incorporating surface energetical heterogeneity and geometrical corrugation