Abstract
A fundamental understanding of acidity at an interface, as mediated by structure and molecule-surface interactions, is essential to elucidate the mechanisms of a range of chemical transformations. While the strength of an acid in homogeneous gas and solution phases is conceptually well understood, acid-base chemistry at heterogeneous interfaces is notoriously more complicated. Using density functional theory and nonlinear vibrational spectroscopy, we present a method to determine the interfacial Brønsted-Lowry acidity of aliphatic alcohols adsorbed on the (100) surface of the model perovskite, strontium titanate. While shorter and less branched alkanols are known to be less acidic in the gas phase and more acidic in solution, here we show that shorter alcohols are less acidic whereas less substituted alkanols are more acidic at the gas-oxide interface. Hydrogen bonding plays a critical role in defining acidity, whereas structure-acidity relationships are dominated by van der Waals interactions between the alcohol and the surface.
| Original language | English |
|---|---|
| Pages (from-to) | 23478-23485 |
| Number of pages | 8 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 23 |
| Issue number | 41 |
| DOIs | |
| State | Published - Nov 7 2021 |
Funding
Computations of the adsorption steps of isopropanol on STO(100) were supported by the UT-ORNL Joint Directed Research and Development (JDRD) Program of the Tennessee Science Alliance. Computations of the adsorption steps on other alkanols on STO(100) and calculations of interfacial acidity were supported by the National Science Foundation CAREER grant CHE-1753273. Computations were performed using resources at the Center for Functional Nanomaterials, a U.S. DOE Office of Science Facility, and the Scientific Data and Computing Center, a component of the Computational Science Initiative, at Brookhaven National Laboratory under Contract No. DE-SC0012704. A. U. C. and B. D. were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. R. L. S. was supported by the Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. S. R. thanks John E. Bartmess for discussions on alcohol acidity in gaseous and aqueous phases. † This manuscript has been authored 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 non-exclusive, paid-up, irrevocable, 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). ‡ Electronic supplementary information (ESI) available: Computations of STO surface stability, adsorption potential-energy-surface scan, alkanol adsorption structural and vibrational frequency data, discussion of van der Waals interactions and interfacial acidity, experimental X-ray diffraction, atomic force microscopy surface characterization data, separate file containing the atomic coordinates of all DFT-optimized structures. See DOI: 10.1039/d1cp03587h