STUDIES IN THE ELECTROCHEMISTRY OF DISSOLVING MICRODROPLETS AND AQUEOUS BATTERIES

This dissertation presents two complementary research directions unified by a central theme: understanding chemical reactivity in confined, dynamically evolving, and kinetically complex electrochemical environments. The first part introduces dissolving-droplet electrochemistry as a new measurement paradigm for probing redox processes under transient geometries and extreme confinement. Using ultramicroelectrodes as both structural supports and sensing platforms, the work establishes the first electrochemical-computational framework capable of reconstructing droplet geometry and dissolution dynamics from electrochemical signals alone. This platform enables precise determination of liquid in liquid diffusion coefficients, reveals nanometer-scale motion of dissolving droplets, and leverages spontaneous droplet shrinkage for analyte enrichment. These principles are extended to develop electroanalytical strategies achieving sub-nanomolar, attomolar, and even near–single-molecule detection through partitioning-driven enrichment, catalytic amplification, and biphasic redox cycling.The second part advances the fundamental electrochemistry governing aqueous zinc-metal batteries, with emphasis on quantifying the intertwined processes of zinc electrodeposition, hydrogen evolution, and corrosion. Fast-scan voltammetry on ultramicroelectrodes is used to isolate intrinsic charge-transfer kinetics, exposing limitations of classical Tafel analysis and introducing improved kinetic frameworks. Operando electrochemical mass spectrometry enables direct quantification of hydrogen evolution during zinc deposition, revealing its small yet cumulatively detrimental contribution to anode degradation. Mechanistic studies identify the chemical origin of hydrogen evolution in coordinated water reduction, rationalize electrolyte-dependent performance trends, and inspire solvation-shell engineering strategies that suppress parasitic reactions. Additional efforts quantify intrinsic hydrogen evolution activity of common current collectors and resolve paradoxical improvements in coulombic efficiency at high current densities through interfacial pH gradients. Finally, the mechanistic origin of resting losses is established by demonstrating lateral electron-exchange pathways and galvanic coupling across cell hardware components.Together, these contributions provide new electrochemical tools, mechanistic insights, and design principles that expand the scope of measurement science in confined systems and advance the development of stable, high-performance aqueous zinc-metal batteries.