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Lu Yu Dissertation FINAL-120516.pdf (12.58 MB)

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Application of Lead Underpotential Deposition for the Characterization of Heterogeneous Surfaces in Electrochemical Systems

Yu, Lu
http://rave.ohiolink.edu/etdc/view?acc_num=case1480934595431209

Abstract Details

2017, Doctor of Philosophy, Case Western Reserve University, Chemical Engineering.
Heterogeneous surfaces are commonly encountered in electrochemical systems. For example, in semiconductor interconnect metallization, electrochemical deposition of copper (Cu) directly onto a noble metal substrate such as ruthenium (Ru) is employed for fabricating conductive Cu seed layers. During the early stages of electronucleation of Cu on Ru, the substrate surface is heterogeneous, i.e., comprising of the Ru substrate with only a partial surface coverage of deposited Cu. In applications based on electrocatalysis, heterogeneous surfaces of binary alloy electrocatalysts provide enhanced electrocatalytic activity, improved selectivity and stability. An example of alloy electrocatalyst used for glucose oxidation is silver–gold (Ag–Au), which exhibits high catalytic activity for this reaction in alkaline media. The surface composition of the Ag–Au catalyst plays an important role in enhancing its activity for glucose oxidation and thus precise quantification of the surface composition is essential for optimal catalyst design. In the present work, heterogeneous surfaces comprising of Cu–Ru and Ag–Au are investigated using an electrochemical technique based on the underpotential deposition of lead (Pbupd). At suitable electrode potentials, underpotential deposition enables the formation of a self-limiting adlayer of Pb atoms onto the `foreign’ electrode surface. The self-limiting behavior is due to the energetically favored interactions between the depositing Pb atoms and the substrate surface. For binary Cu–Ru alloy surfaces, selective Pbupd on Ru surface sites or on Cu surface sites was achieved through electrode potential control. Coulometry during Pbupd formation then provides charge densities associated with Pbupd on Cu and Pbupd on Ru. These charge densities are proportional to the surface fraction (coverage) of each alloy component, thereby providing direct and quantitative surface characterization of the Cu–Ru surface. In the work reported herein, the Pbupd based surface characterization technique enabled quantitative measurement of the Cu surface coverage evolution during the early stages of electroless Cu deposition onto Ru. The Pbupd technique, combined with anodic stripping coulometry of the electroless deposits, confirmed that electroless deposition of Cu on Ru proceeds via two-dimensional growth. Cu islands eventually coalesce leading to the formation of a single atomic layer of Cu on Ru during the early stages of electronucleation. The phenomenon of two-dimensional growth during early stage nucleation is also shown to occur during electrodeposition of Cu onto Ru. The effect of surface alloy composition on the activity of Ag–Au electrocatalysts towards the glucose oxidation reaction was also investigated using Pbupd. Here too, the surface sensitive nature of Pbupd enabled accurate determination of the optimal surface alloy composition (Ag0.56Au0.44) that provides fastest glucose oxidation kinetics.
Rohan Akolkar (Committee Chair)
Uziel Landau (Committee Member)
Mohan Sankaran (Committee Member)
Geneviève Sauvé (Committee Member)
136 p.
Chemical Engineering
Underpotential deposition; Heterogeneous surfaces; Electronucleation; Electrocatalysts

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Citations

  • Yu, L. (2017). Application of Lead Underpotential Deposition for the Characterization of Heterogeneous Surfaces in Electrochemical Systems [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1480934595431209

    APA Style (7th edition)

  • Yu, Lu. Application of Lead Underpotential Deposition for the Characterization of Heterogeneous Surfaces in Electrochemical Systems . 2017. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1480934595431209.

    MLA Style (8th edition)

  • Yu, Lu. "Application of Lead Underpotential Deposition for the Characterization of Heterogeneous Surfaces in Electrochemical Systems ." Doctoral dissertation, Case Western Reserve University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1480934595431209

    Chicago Manual of Style (17th edition)

case1480934595431209
2,134
© 2017, some rights reserved.Creative Commons License Application of Lead Underpotential Deposition for the Characterization of Heterogeneous Surfaces in Electrochemical Systems by Lu Yu is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.