Electrochemical reactions on the nanoscale play a pivotal role in a variety of areas, including electrocatalysis, energy conversion and storage, corrosion prevention, plasmon driven chemistry, and so forth. An in-depth knowledge of how site-specific compositions and morphologies locally affect the electron transfer kinetics will greatly benefit the design of catalysts, batteries, molecular devices, solar cells, fuel cells, and sensors. To access such information, we integrated tip-enhanced Raman spectroscopy (TERS) with electrochemical scanning tunneling microscopy (EC-STM) to combine electrochemical tunability with single-molecule chemical identification and Ångstrom-scale topographic and chemical imaging. This dissertation presents the development of electrochemical TERS (EC-TERS) based on an EC-STM platform and its applications in the investigations of nanoscale redox reactions and tip functionalization processes. Chapter 1 provides an introductory review of TERS with an emphasis on the current status of EC-TERS. Chapter 2 details an EC-STM-TERS study of redox reactions of Nile Blue covalently tethered on Au(111). Chapter 3 demonstrates the unique capability of EC-STM-TERS to independently monitor redox reactions of tip- and substrate-bound molecules by separately tuning the tip and sample potentials. Chapter 4 elucidates a novel strategy to reversibly functionalize STM tips with adsorbates at the solid-liquid interfaces and its operando observation via EC-TERS. Chapter 5 employs EC-STM-TERS to investigate the electron transfer reactions of cobalt phthalocyanine (CoPc) on Au(111) and CoPc-catalyzed oxygen reduction reactions (ORR). Chapter 6 covers the advances in tip-enhanced Raman excitation spectroscopy (TERES) towards a fundamental understanding of the plasmonic resonance of tip-sample junctions in both ambient and aqueous environments. Taken together, the experimental advances included in this dissertation greatly expand the capabilities of TERS for in situ characterization of nanoscale electrochemical processes and paves the way towards unraveling the heterogeneous electron transfer kinetics and structure-activity relationships with atomic resolution and single-molecule sensitivity.

Creator

• Chen, Xu

DOI

• https://doi.org/10.21985/n2-ecn1-md46

Subject

• Physical chemistry
• Applied physics
• Analytical chemistry

Language

• en

Alternate Identifier

• http://dissertations.umi.com/northwestern:14437
• etdadmin_upload_625491

Keyword

• Tip-Enhanced Raman Spectroscopy
• Nanoscale
• Scanning Tunneling Microscopy
• Electrochemistry
• Tip Functionalization
• Solid-Liquid Interface

Date created

• 2018-01-01

Resource type

• Dissertation

Rights statement

• In Copyright