Probing Electrochemical Processes of Single Entities at the Electrode/Solution Interface

Abstract

This dissertation presents the development and application of new experimental tools and methods for studying single-entity (such as nanoparticles, molecules, and nanobubbles) electrochemistry. Compared to traditional ensemble methods, the ability to probe electrochemical properties and processes of single entities enables one to remove ensemble averaging in understanding their intrinsic heterogeneitiy at the electrochemical interface. Chapter 1 introduces advanced nanoelectrodes in nanoscale electroanalytical chemistry, single-nanoparticle electrochemistry, and single-molecule electrochemistry. Chapter 2 and 3 discuss the development of a unique electrochemical nanocell for imaging single nanoparticles and single molecules. Chapter 2 focuses on studying the dynamic collision and oxidation process of single silver nanoparticles at the electrode/solution interface. Chapter 3 discusses using the electrochemical nanocell and fluorescence to detect single redox molecules. We believe that the use of a nanocell and single molecule/nanoparticle fluorescence microscopy can be extended to other systems to yield highly dynamic information about the electrochemical interface. Chapter 4 demonstrates the direct study of Faradaic processes of single freely diffusing redox molecules on an indium–tin oxide (ITO) electrode coated with mesoporous silica. The use of electrodeposited mesoporous silica reduced the rate of diffusion of fluorogenic redox molecules enabling real-time imaging of single redox events with total-internal reflection fluorescence (TIRF) microscopy. Chapter 5 describes the use of fluorescence microscopy to image the dynamic nucleation and growth of single hydrogen nanobubbles at the electrode/solution interface during electrochemical water splitting. This method is based upon a single-molecule labeling process and it allows us to compare electrocatalytic activity of different electrode materials toward hydrogen evolution reaction.