| Abstract
| - In this work, we propose an improvement of the classical Derjaguin−Broekhoff−de Boer (DBdB) theoryfor capillary condensation/evaporation in mesoporous systems. The primary idea of this improvement isto employ the Gibbs−Tolman−Koenig−Buff equation to predict the surface tension changes in mesopores.In addition, the statistical film thickness (so-called t-curve) evaluated accurately on the basis of the adsorptionisotherms measured for the MCM-41 materials is used instead of the originally proposed t-curve (to takeinto account the excess of the chemical potential due to the surface forces). It is shown that the aforementionedmodifications of the original DBdB theory have significant implications for the pore size analysis ofmesoporous solids. To verify our improvement of the DBdB pore size analysis method (IDBdB), a seriesof the calcined MCM-41 samples, which are well-defined materials with hexagonally ordered cylindricalmesopores, were used for the evaluation of the pore size distributions. The correlation of the IDBdB methodwith the empirically calibrated Kruk−Jaroniec−Sayari (KJS) relationship is very good in the range ofsmall mesopores. So, a major advantage of the IDBdB method is its applicability for small mesopores aswell as for the mesopore range beyond that established by the KJS calibration, i.e., for mesopore radiigreater than ∼4.5 nm. The comparison of the IDBdB results with experimental data reported by Krukand Jaroniec for capillary condensation/evaporation as well as with the results from nonlocal densityfunctional theory developed by Neimark et al. clearly justifies our approach. Note that the proposedimprovement of the classical DBdB method preserves its original simplicity and simultaneously ensuresa significant improvement of the pore size analysis, which is confirmed by the independent estimation ofthe mean pore size by the powder X-ray diffraction method.
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