Free Energies of Catalytic Species Adsorbed to Pt(111) Surfaces under Liquid Solvent Calculated Using Classical and Quantum Approaches

Xiaohong Zhang, Ryan S. Defever, Sapna Sarupria, Rachel B. Getman

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

Solvent plays an important role in liquid phase heterogeneous catalysis; however, methods for calculating the free energies of catalytic phenomena at the solid-liquid interface are not well-established. For example, solvent molecules alter the energies of catalytic species and participate in catalytic reactions and can thus significantly influence catalytic performance. In this work, we begin to establish methods for calculating the free energies of such phenomena, specifically, by employing an explicit solvation method using a multiscale sampling (MSS) approach. This MSS approach combines classical molecular dynamics with density functional theory. We use it to calculate the free energies of solvation of catalytic species, specifically adsorbed NH∗, NH2∗, CO∗, COH∗, CH2OH∗, and C3H7O3∗ on Pt(111) surfaces under aqueous phase and under a mixed H2O/CH3OH solvent. We compare our calculated values with analogous values from implicit solvation for validation and to identify situations where implicit solvation is sufficient versus where explicit solvent is needed to compute adsorbate free energies. Our results indicate that explicit quantum-based methods are needed when adsorbates form chemical bonds and/or strong hydrogen bonds with H2O solvent. Using MSS, we further separate the calculated free energies into energetic and entropic contributions in order to understand how each influences the free energy. We find that adsorbates that exhibit strong energies also exhibit strong and negative entropies, and we attribute this relationship to hydrogen bonding between the adsorbates and the solvent molecules, which provides a large energetic contribution but reduces the overall mobility of the solvent.

Original languageEnglish (US)
Pages (from-to)2190-2198
Number of pages9
JournalJournal of Chemical Information and Modeling
Volume59
Issue number5
DOIs
StatePublished - May 28 2019
Externally publishedYes

Bibliographical note

Funding Information:
This research was funded by the National Science Foundation under grant numbers CBET-1554385 (Getman) and AGS- 1541944 (Sarupria). Simulations were performed on the Palmetto Supercomputer Cluster, which is maintained by the Cyberinfrastructure Technology Integration Group at Clemson University. We thank Dr. Steven Louis Pellizzeri, who worked as a postdoctoral associate in our group, for helpful discussions about charge density analysis, and Anna Hardymon, who was an undergraduate intern in our group through the Clemson University EURKEA! program, for testing the influence of simulation box size on ΔEintMD.

Publisher Copyright:
© 2019 American Chemical Society.

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