Micromeritics Instrument Corporation, 4356 Communications Drive, Norcross, GA 30093, United States.
Micromeritics Instrument Corporation, 4356 Communications Drive, Norcross, GA 30093, United States.
J Colloid Interface Sci. 2019 Apr 15;542:151-158. doi: 10.1016/j.jcis.2019.01.116. Epub 2019 Feb 1.
The pore size distribution (PSD) of porous carbons is most often derived from the analysis of standard N and Ar adsorption isotherms measured at 77 and 87 K. From the two gases, Ar is recommended (IUPAC Technical Report 2015) as more reliable for the PSD analysis due to its minimal specific interactions with the surface polar groups. Such interactions may influence the adsorption of N molecules due to its significant quadrupole moment. In practice, however, using liquid Ar as a cryogen for Ar adsorption measurements may be challenging because of its high cost and limited availability in various parts of the world. In this study, we propose using O adsorption isotherms for the PSD characterization of porous carbons. The quadrupole moment of O is less than one-third of the value reported for N, and thus its susceptibility to specific interactions with polar groups is much smaller than that of N. We demonstrate a quantitative agreement between the PSD results derived from the adsorption isotherms of O and N measured at 77 K, and Ar at 87 K on four representative carbon samples. The PSD calculations are performed using adsorption models based on the two-dimensional non-local density functional theory (2D-NLDFT).
多孔碳的孔径分布（PSD）通常是通过分析在 77 和 87 K 下测量的标准 N 和 Ar 吸附等温线得出的。在这两种气体中，由于其与表面极性基团的最小特异性相互作用，Ar 被推荐（IUPAC 技术报告 2015）更可靠用于 PSD 分析。这种相互作用可能会影响 N 分子的吸附，因为 N 分子具有显著的四极矩。然而，在实践中，由于其高昂的成本和在世界不同地区的有限可用性，使用液体 Ar 作为 Ar 吸附测量的制冷剂可能具有挑战性。在这项研究中，我们提出使用 O 吸附等温线来表征多孔碳的 PSD。O 的四极矩小于 N 的报告值的三分之一，因此其与极性基团特异性相互作用的敏感性比 N 小得多。我们证明了在四个代表性碳样品上，在 77 K 下测量的 O 和 N 的吸附等温线以及在 87 K 下测量的 Ar 的 PSD 结果之间存在定量一致性。PSD 计算是使用基于二维非局部密度泛函理论（2D-NLDFT）的吸附模型进行的。
