A Caltech Library Service

Temperature Dependence of Gas Physisorption Energy: Experimental and Computational Studies of Krypton on Porous Carbon


Wang, Ziyi (2023) Temperature Dependence of Gas Physisorption Energy: Experimental and Computational Studies of Krypton on Porous Carbon. Dissertation (Ph.D.), California Institute of Technology.


This work comprehensively investigated the temperature dependence of physical adsorption energy, combining theoretical, computational, and experimental approaches. A thermodynamic analysis of the 2D ideal gas and the slit-pore models highlighted the role of van der Waal potentials in the adsorption energy and isotherm fitting methods, especially Henry's law. Experimental data of krypton adsorption on CNS-201 and MSC-30 porous carbon materials revealed a significant weakening in the isosteric adsorption energy with temperatures from 250 K to 330 K. Using the zero-coverage Henry's constants and Clausius–Clapeyron equation, the adsorption energies weaken for 13% and 15% for CNS-201 and MSC-30. The corresponding changing rates are 4.35k_B for CNS-201 and 3.65k_B for MSC-30.

The DFT-based computational study with the slit-pore model showed the van der Waal potentials of different-sized pores. Then it showed how the structures of the pores significantly influence the surface dynamics and the internal energies of the adsorbates at different temperatures. Gas molecules adsorbed in pores of different sizes have different heat capacities larger than the gas phase, leading to a temperature dependence of adsorption energy. Monte Carlo calculation indicated that displacements of adsorbent atoms caused by thermal vibration slightly weaken the van der Waal potentials but have a negligible effect on the temperature dependence of the adsorption energy.

The distribution of pore sizes plays a crucial role in the temperature dependence of the overall adsorption energy. With increasing temperature, the pores with higher energy states become more accessible due to the Boltzmann distribution, weakening the statistically averaged internal energy. Adsorption energy weakening of 5% and 15% for CNS-201 and MSC-30 are given by combining the computational van der Waal potentials and experimentally measured pore sizes. The changing rates are 0.62k_B and 2.03k_B.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:adsorption; thermodynamic; density functional theory; porous carbon; krypton
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Fultz, Brent T.
Thesis Committee:
  • Goddard, William A., III (chair)
  • Wang, Zhen-Gang
  • Stadie, Nicholas
  • Fultz, Brent T.
Defense Date:3 April 2023
Non-Caltech Author Email:zywang0719 (AT)
Record Number:CaltechTHESIS:05162023-225200255
Persistent URL:
Wang, Ziyi0000-0003-0811-921X
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15181
Deposited By: Ziyi Wang
Deposited On:26 May 2023 22:26
Last Modified:02 Jun 2023 23:06

Thesis Files

[img] PDF - Final Version
See Usage Policy.


Repository Staff Only: item control page