University of Illinois Urbana-Champaign

In Situ Structural Study of Underpotential Deposition and Electrocatalysis on Gold(111) Electrodes

Chen, Chun-Hsien

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Description

Title
In Situ Structural Study of Underpotential Deposition and Electrocatalysis on Gold(111) Electrodes
Author(s)
Chen, Chun-Hsien
Issue Date
1993
Doctoral Committee Chair(s)
Gewirth, Andrew A.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • Chemistry, Analytical
  • Chemistry, Physical
  • Physics, Condensed Matter
Abstract
  • This thesis work has studied systems of Bi, Pb, Ag, and Hg underpotential deposition (UPD) on Au(111) electrodes. The application of the atomic force microscope (AFM), the scanning tunneling microscope (STM), and the surface x-ray scattering (SXS) to these UPD studies has provided in situ measurements from which we investigate factors that determine UPD surface structures and correlate these structures with surface reactivity.
  • For all the UPD systems in this thesis work, atomic level features of the electrode surface have been revealed. In the case of Pb UPD, Pb starts to deposit by forming islands which exhibit a hexagonal close packed structure of Pb adatoms, while, in the other systems, the UPD adatoms form open lattices. In the Bi and Pb studies, we correlate the activities of the modified surface toward electroreduction of $\rm H\sb2O\sb2$ with the adlattice structures. A heterobimetallic bridge model for $\rm H\sb2O\sb2$ on the surface could explain the enhanced reactivity. The full monolayers of Bi and Hg, rhombohedral metals, form rectangular lattice structures on the hexagonal Au(111) surfaces. The partial charge retention on the Bi and Hg adatom opens the adlayer structure when the coverage is less than a full monolayer. The structure of the first submonolayers of Ag UPD is electrolyte-dependent. The electrode surface exhibits 3 x 3 and 4 x 4 overlayer structures in solutions containing sulfate and nitrate, respectively. In perchloric acid another open structure is observed and a close-packed monolayer is formed in acetic acid. The different monolayer structures give rise to packing densities which correlate with electrolyte size. This implies that the anions participate in reducing metal ions.
Graduation Semester
1993
Type of Resource
text
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http://hdl.handle.net/2142/72282

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