Methane Adsorption on Heteroatom-Modified Maquettes of Porous Carbon Surfaces

Rylan Rowsey, Erin E. Taylor, Stephan Irle, Nicholas P. Stadie, Robert K. Szilagyi

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Experimental and theoretical studies disagree on the energetics of methane adsorption on carbon materials. However, this information is critical for the rational design and optimization of the structure and composition of adsorbents for natural gas storage. The delicate nature of dispersion interactions, polarization of both the adsorbent and the adsorbate, interplay between H-bonding and tetrel bonding, and induced dipole/Coulomb interactions inherent to methane physisorption require computational treatment at the highest possible level of theory. In this study, we employed the smallest reasonable computational model, a maquette of porous carbon surfaces with a central site for substitution and methane binding. The most accurate predictions of methane adsorption energetics were achieved by electron-correlated molecular orbital theory CCSD(T) and hybrid density functional theory MN15 calculations employing a saturated, all-electron basis set. The characteristic geometry of methane adsorption on a carbon surface ("lander approach") arises due to bonding interactions of the adsorbent I -system with the proximal H-C bonds of methane, in addition to tetrel bonding between the antibonding orbital of the distal C-H bond and the central atom of the maquette (C, B, or N). The polarization of the electron density, structural deformations, and the comprehensive energetic analysis clearly indicate a â 3 kJ mol-1 preference for methane binding on the N-substituted maquette. The B-substituted maquette showed a comparable or lower binding energy than the unsubstituted, pure C model, depending on the level of theory employed. The calculated thermodynamic results indicate a strategy for incorporating electron-enriched substitutions (e.g., N) into carbon materials as a way to increase methane storage capacity over electron-deficient (e.g., B) modifications. The thermochemical analysis was revised for establishing a conceptual agreement between the experimental isosteric heat of adsorption and the binding enthalpies from statistical thermodynamics principles.

Original languageEnglish
Pages (from-to)6042-6058
Number of pages17
JournalJournal of Physical Chemistry A
Volume125
Issue number28
DOIs
StatePublished - Jul 22 2021

Funding

This manuscript has been coauthored by UT-Battelle, LLC under contract no. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, and world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). Acknowledgments R.R., E.E.T., and N.P.S. are supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Hydrogen and Fuel Cell Technologies and Vehicle Technologies Offices (DE-EE0008815). S.I. acknowledges support for the analysis of theoretical results by the U.S. Department of Energy Fossil Energy and Carbon Management Program, Advanced Coal Processing Program, C4WARD project. N.P.S. acknowledges the donors of the American Chemical Society Petroleum Research Fund for partial support of this research. R.R. is thankful for the support by the MSU Undergraduate Scholars Program. We are also grateful for resources provided by the Extreme Science and Engineering Discovery Environment (XSEDE), supported by National Science Foundation grant ACI-1548562. Part of the computations were carried out using the Hyalite High Performance Computing System, operated and supported by the University Information Technology Research Cyberinfrastructure at Montana State University.

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