Electrochemical vibrational characterization of metal nanoelectrodes
Abstract
Infrared reflection-absorption spectroscopy (IRAS) and Surface-enhanced Raman spectroscopy (SERS) have been employed as an in-situ probe of adsorbate structure and bonding at metal nanoparticles under electrochemical environments. Understanding how the chemical coordinative and catalytic properties of metal nanoparticles depend on their size and shape is of considerable current interest. We have characterized carbon supported platinum nanoparticle systems, “real-world catalysts”, by means of in-situ IR spectroscopy along with conventional electrochemistry, utilizing carbon monoxide (CO) as a probe molecule. The dependence of spectral properties of CO on particle size in the range 2 to 10 nm can be explained in terms of population transition of surface terrace sites to edge or vertex sites, which is related to alterations in the local surface density of states. The electrocatalytic rate dependence of methanol, formic acid and formaldehyde on the particle size is observed when the effective surface is normalized. The nanoparticle size-sensitivity for these related yet distinct electrocatalytic processes will be interpreted in terms of nanostructural ensemble effects. Given the marked dependence of Pt nanoparticle electrocatalytic properties on the particle size, a bimetallic system of ruthenium-decorated Pt nanoparticles has been explored with the objective of unveiling the electrocatalytic effects of promoter (Ru) surface concentrations on CO electrooxidation. Also discussed will be a novel use of gold nanoparticles as a template to synthesize Pt-coated nanostructures, leading to the generalization of surface-enhanced Raman scattering application to other important catalytic processes.
Degree
Ph.D.
Advisors
Weaver, Purdue University.
Subject Area
Analytical chemistry|Chemistry
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