Analysis of Carbon Materials Porosity by Simultaneous Use of Adsorption Data for Nitrogen and Carbon Dioxide

Knowledge of porous structure of carbons, including ultramicropores, micropores and mesopores, is of great importance in application of these materials for different purposes. Usually, their characteristics includes determination of specific surface area, pore volume and pore size distribution. The latter is often calculated on the basis of experimental nitrogen adsorption isotherm at 196 degrees C for relative pressures ranging from about 10(-7) up to 1.0. It has been determined that experimental CO2 adsorption isotherm alone (0 degrees C, up to 1 atm), or together with N-2 adsorption isotherm, may be applied to yield interesting results of pore size distributions. For illustration purposes, the pore size distributions were calculated for the three polymer-obtained microporous carbons and one ordered mesoporous carbon obtained by soft templating. The calculations were performed using the latest version of the SAIEUS program based on the Nonlinear Method in the Density Functional Theory (NLDFT) for the non-uniformly porous carbon materials. It has been shown that the simultaneous use of N-2 and CO2 adsorption isotherms for calculation of the pore size distribution allows for a realistic assessment of carbon materials porosity.