Abstract

This dissertation presents an integrative study of molecular and device-level engineering strategies in advanced electrochemical energy technologies, addressing key challenges across organic redox flow batteries (ORFBs), direct methanol hydrogen peroxide fuel cells (DMHPFCs), and electrochemical hydrogen pumps (EHPs). First, the influence of electrolyte pH and salt anion chemistry on redox-active organic cations (BTMAP-Fc and BTMAP-Vi) is elucidated, identifying solvent reorganizational energy (λ) as a universal descriptor for optimal electrolyte selection in ORFBs. Detailed characterization reveals that low pH methanesulfonate or chloride counterions offer superior balance of kinetic and transport properties, facilitating efficient energy storage using earth-abundant elements. Second, a modified kinetic analysis framework—adjusted Koutecky-Levich (A-K-L) equation—is developed to unravel parallel reaction pathways in the hydrogen peroxide electroreduction reaction (HPRR), surpassing the limitations of classical single-pathway models. Hydrodynamic chronocoulometry and electrode screening demonstrate that gold-based catalysts excel at selective 2-electron H2O2 reduction, providing mechanistic clarity and a practical toolkit for rapid electrocatalyst optimization toward fuel cell applications. Third, the concept of pH-gradient-enabled microscale bipolar interfaces (PMBI) is introduced for direct methanol hydrogen peroxide fuel cells (DMHPFCs), enabling simultaneous operation of alkaline and acidic environments at the anode and cathode, respectively. This configuration realizes a high theoretical open-circuit voltage (1.72 V) and quadrupled energy density compared to compressed hydrogen systems, although it also highlights the impact of mass transport limitations and membrane crossover on practical performance. This study identifies optimal anolyte and catholyte concentration, membrane thickness and flow rate to maximize the power output and minimize activation-, ohmic-and mass transfer losses. Finally, new operational protocols are proposed for low-temperature electrochemical hydrogen pumps (LT-EHPs) under CO contamination, a major barrier to hydrogen purification scalability. Advanced pulse oxidation strategies—particularly dynamic, voltage-triggered pulsing—are shown to deliver sustained catalyst regeneration, boosting separation and energy efficiency by over 10–15% compared to conventional approaches. Five-day continuous testing confirms the robustness of these methods for impurity-resilient, modular hydrogen purification. Collectively, these studies establish universally applicable molecular descriptors, introduce mechanistically precise models for complex reactions, pioneer new interface designs for fuel cell voltage and energy density enhancements, and develop resilient operational strategies for impurity mitigation in hydrogen pumps. This dissertation advances the scientific and technological foundations for next-generation sustainable electrochemical energy system.

Committee Chair

Vijay Ramani

Committee Members

Jian Wang; Shrihari Sankarasubramanian; Srikanth Singamaneni; Yinjie Tang

Degree

Doctor of Philosophy (PhD)

Author's Department

Energy, Environmental & Chemical Engineering

Author's School

McKelvey School of Engineering

Document Type

Dissertation

Date of Award

12-9-2025

Language

English (en)

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