FTIR spectroscopy for the molecular structural characterization of electrode/solution interfaces
Abstract
We have explored several new aspects in the development of external reflectance infrared spectroscopy for the in-situ molecular characterization of electrode/solution interfaces. The majority of this research effort has focussed on the application of potential-difference infrared spectroscopy (PDIRS), as configured for a Fourier transform infrared (FTIR) spectrometer, to the investigation of both stable and reactive intermediates. Although much of the experimental design for this recently developed technique has been established, the advantages and limitations of the method for in-situ interfacial analysis are only presently being realized. Our contributions in this area have fallen into three categories: the application of PDIRS as an analytical probe of anionic and molecular adsorption at mono- and polycrystalline electrode surfaces, as a complementary technique to surface-enhanced Raman spectroscopy (SERS), and as a vibrational probe of redox processes. We have demonstrated that in suitable cases, the frequencies and intensities of the vibrational bands observed in the PDIR spectra cannot only provide a molecule-specific measure of the surface concentration but can yield valuable information concerning adsorbate orientation and interfacial structure as well as the nature of the adsorbate-surface interactions. Whenever possible, surface-coverage data extracted from the PDIR spectra has been compared with the corresponding information obtained from more direct conventional electrochemical methods. PDIRS was found to be a useful method for evaluating the applicability of SERS to the study of adsorbates at silver and gold electrode surfaces. Significant differences as well as similarities, particularly with regard to the peak frequencies, bandwidths and band occurrences for adsorbed species, are observed and discussed for the electrochemical surface vibrational spectra obtained by these two techniques. PDIRS has also been employed in the investigation of the role of adsorbed species in irreversible as well as reversible electrode reaction mechanisms at platinum and gold electrodes. Considerable attention has been given to the role of adsorbed CO in the electrooxidation of organic fuels such as methanol and formic acid at platinum.
Degree
Ph.D.
Advisors
Weaver, Purdue University.
Subject Area
Analytical chemistry
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