Dissertations, Theses, and Capstone Projects
Date of Degree
2-2026
Document Type
Doctoral Dissertation
Degree Name
Doctor of Philosophy
Program
Chemistry
Advisor
Michael V. Mirkin
Committee Members
Uri Samuni
Hiroshi Matsui
Elisa M. Miller
Subject Categories
Analytical Chemistry | Chemistry | Materials Chemistry | Nanoscience and Nanotechnology | Physical Chemistry | Semiconductor and Optical Materials
Keywords
Scanning electrochemical microscopy (SECM), tunneling-mode photo SECM, charge-transfer kinetics, photocatalysis, electrocatalysis, semiconductor interfaces
Abstract
Scanning electrochemical microscopy (SECM) has become an indispensable technique for resolving charge-transfer processes with micro- to nanometer spatial precision. This dissertation advances SECM and its photoactive variants as powerful tools for interrogating electrochemical and photoelectrochemical phenomena across catalytic nanostructures, semiconductor interfaces, and complex photocatalytic architectures. The work begins with fundamental principles of nanoelectrode behavior and SECM operation (Chapter 1), establishing the theoretical and instrumental foundation required for high-resolution electrochemical imaging. Building on these fundamentals, Chapter 2 examines heterogeneous photocatalysts using advanced electrochemical scanning probe microscopies, integrating amperometric and potentiometric modalities to map activity, charge separation, and interfacial energetics.
In Chapter 3, we extend the tunneling mode of SECM to characterize charge-transfer kinetics at single metallic, pseudo-metallic, and semiconducting nanoparticles. Using ultrathin carbon nanoelectrodes, this work enables single-nanoflake voltammetry without ohmic contact, revealing intrinsic catalytic behavior in MoS2 phases, porous carbon catalysts, and MXene nanosheets. Chapter 4 applies both diffusion-based and tunneling-based photo-SECM to nanoscale photocatalysts, achieving spatial resolutions down to 1–2 nm. These measurements reveal local photocurrent generation, hydrogen evolution, and active-site heterogeneity in mixed-phase 2D materials and CVD-grown semiconductors.
Chapter 5 demonstrates the combined amperometric and potentiometric photo-SECM analysis of Pt/TiO2 photocatalysts, capturing nanoscale variations in photogenerated charge carriers, catalytic turnover, and interfacial potentials under operando conditions. Finally, Chapter 6 integrates SECM imaging with simplified band-structure modeling to construct an electrochemical geometry-programmed photocatalyst of GaInP/GaN photocathodes functionalized with spatially separated IrOx and Rh–CrOx cocatalysts. Using Substrate Generation/Tip Collection and tunneling-distance potentiometric SECM, we directly probe and map local oxygen and hydrogen evolution, catalyst-dependent band bending, and interfacial Fermi-level shifts with nanometer precision.
Together, this dissertation establishes a unified framework for probing, understanding, and engineering charge-transfer processes at the nanoscale. The integrated use of tunneling SECM, photo-SECM, and digital-twin modeling provides mechanistic insight essential for the rational design of next-generation catalysts and semiconductor materials for solar energy conversion, providing a general operando framework for designing and diagnosing next-generation photocatalysts.
Recommended Citation
Bo, Tianyu, "Nanoscale Probing of Electrochemical Processes on Photocatalytic Materials by Tunneling Mode Photo-Scanning Electrochemical Microscopy" (2026). CUNY Academic Works.
https://academicworks.cuny.edu/gc_etds/6538
Included in
Analytical Chemistry Commons, Materials Chemistry Commons, Nanoscience and Nanotechnology Commons, Physical Chemistry Commons, Semiconductor and Optical Materials Commons
