Electrochemical vibrational spectroscopy: Fundamental insight from density functional theory calculations
Abstract
The application of Density Functional Theory (DFT) to electrochemical vibrational spectroscopy, using variable-field finite-cluster and periodic-slab models of surface-chemisorbate bonding, is considered, with the particular objective of developing a more complete understanding of how the experimentally accessible electrode-, adsorbate- and potential-dependent (i.e., Stark-tuning) vibrational frequency is a measure of specific chemical properties not accessible to experiment in electrochemical systems, such as the nature of the surface-adsorbate orbital and electron-transfer interactions, adlayer structure, bond geometry and binding energy. The field dependence of the bonding and vibrational properties of several archetypical adsorbates are examined, including the surface-adsorbate and intramolecular vibrations of carbon monoxide on Pt-group (111) surfaces and the surface-adsorbate vibrations of halogens, other monoatomic adsorbates and ammonia. A general classification between the nature of the surface-adsorbate interaction (i.e., electron donation or withdrawal and covalent or ionic) and the sign of the field-dependent binding energy and vibrational frequency slopes is presented so that interpretation or misinterpretation of potential-dependent vibrational frequencies in terms of bond lengths can be recognized. The relationships (or lack thereof) between vibrational frequency, binding energy and bond length for electrode-adsorbate interactions are also established. In addition to bonding properties of surface-adsorbate interactions, other aspects of electrochemical vibrational spectroscopy are explored, including vibrational band assignments and interpretation of the complex spectra of benzonitrile bound to Pt-group and coinage-metal surfaces, infrared and Raman vibrational band intensity predictions for various surface-adsorbate bonds, and influences of solvent coadsorption on the vibrational behavior of carbon monoxide on Pt(111) so that spectral differences in electrochemical and ultrahigh vacuum environments can be appreciated.
Degree
Ph.D.
Advisors
Weaver, Purdue University.
Subject Area
Analytical chemistry|Chemistry
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