https://scholars.lib.ntu.edu.tw/handle/123456789/611497
標題: | Assessing the Surface Area of Porous Solids: Limitations, Probe Molecules, and Methods | 作者: | De Lange M.F. Lin L.-C. Gascon J. Vlugt T.J.H. Kapteijn F. LI-CHIANG LIN |
關鍵字: | Activated carbon;Adsorbates;Adsorption;Carbon;Characterization;Geometry;Graphene;Nitrogen;Pore size;Probes;Specific surface area;Adsorbate molecules;Applied analysis;Geometric surface area;Graphitic materials;Indistinguishability;Large surface area;Multilayer formation;Probe molecules;Molecules | 公開日期: | 2016 | 卷: | 32 | 期: | 48 | 起(迄)頁: | 12664-12675 | 來源出版物: | Langmuir | 摘要: | In this modeling study, the uses of nitrogen (77.3 K), probe molecule of choice for decades, and argon, opted as alternative in the 2015 IUPAC report on adsorptive characterization, as probe molecules for geometric surface area determination are compared. Graphene sheets possessing slit-shaped pores with varying size (width) are chosen as model porous solids, and different methods for the determination of specific surface areas are investigated. The BET method, which is the most commonly applied analysis, is compared to the Langmuir and relatively recently proposed ESW (excess sorption work) method. We show that either using argon or nitrogen as adsorptive, the physical meaningfulness of adsorption-derived surface areas highly depends on the pore size. When less than two full layers of adsorbate molecules can be formed within slitlike pores of a graphitic material (Dpore < 5.8 ? for Ar/N2), adsorption-derived surface areas are about half that of the geometric surface area. Between two and four layers (6.8 < Dpore < 12.8 ?), adsorption surface areas can be significantly larger (up to 75%) than the geometric surface area because monolayer-multilayer formation and pore filling cannot be distinguished. For four or more layers of adsorbate molecules (Dpore > 12.8 ?), adsorption-derived surface areas are comparable to their geometrically accessible counterparts. Note that for the Langmuir method this only holds if pore-filling effects are excluded during determination. This occurs in activated carbon materials as well. In the literature, this indistinguishability issue has been largely overlooked, and erroneous claims of materials with extremely large surface areas have been made. Both the BET and Langmuir areas, for Dpore > 12.8 ?, correspond to geometric surface areas, whereas the ESW method yields significantly lower values. For the 6.8 ? < Dpore < 12.8 ? range, all methods erroneously overestimate the specific surface area. For the energetically homogeneous graphene sheets, differences between argon and nitrogen for the assessment of surface areas are minor. ? 2016 American Chemical Society. |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-85002800508&doi=10.1021%2facs.langmuir.6b03531&partnerID=40&md5=32a42f0e08d2e5b0717b1e454c53dc1c https://scholars.lib.ntu.edu.tw/handle/123456789/611497 |
DOI: | 10.1021/acs.langmuir.6b03531 |
顯示於: | 化學工程學系 |
在 IR 系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。