Comprehensive Analysis of Hierarchical Porous Carbons Using a Dual-Shape 2D-NLDFT Model with an Adjustable Slit–Cylinder Pore Shape Boundary

A thorough characterization of the textural properties of hierarchical porous carbons (HPCs) is of utmost importance as it provides information that aids in the selection of a suitable material for a given application and in understanding the phenomena observed once the material becomes part of a system. Gas adsorption-desorption isotherms coupled with the application of density functional theory (DFT) models to these isotherms are common tools for the textural characterization of HPCs, for which pore shape is an essential factor for the determination of pore size distributions (PSDs). By analyzing the experimental adsorption data of a series of CO2-activated HPCs with a progressive development of porosity, it is shown that artifacts are found in the derived PSDs when a slit-cylinder pore shape boundary is fixed at 2 nm, which is the case for the original dual-shape nonlocal DFT (2D-NLDFT-HS) and hybrid quenched solid DFT (QSDFT) models. This study presents a new dual-shape 2D-NLDFT-HS (DS-HS) model that, combined with the 2D-NLDFT-HS model for CO2, provides the possibility of analyzing simultaneously N2 and CO2 adsorption-desorption isotherms and adjusting at the same time the limits for the assumed slit and cylindrical pore shapes. Using the DS-HS approach and adjusting the slit-cylinder boundary at 3 nm allowed eliminating PSDs artifacts. The interactive adjustment of the slit-cylindrical pore shape boundary of the DS-HS model represents a major advantage of this approach allowing for a comprehensive analysis of the adsorption data and a more accurate description of the textural properties of HPC materials.