Doctor of Philosophy, The Ohio State University, 2022, Chemistry

Increasing concerns about carbon emissions has led to the global adoption of renewable energy initiatives. Direct integration of renewable energy sources, however, is difficult because of the intermittency of such sources. Furthermore, direct integration would overload the grid and lead to blackouts. Thus, grid-scale electrical energy storage is required to store and provide energy on-demand. Redox flow batteries have attracted attention as a scalable, inexpensive storage technology. Flow batteries store energy in solvated, redox-active electrolytes, as opposed to conductive, solid materials. These solutions are stored in separated reservoirs and are flowed to the electrochemical cell to cycle the redox-active compound. Energy stored in this fashion decouples energy and power, which allow for increased operational control. While many electrolytes exist, few electrolyte examples have achieved commercialization because of low solubility and low cell voltage. Redox-targeting flow batteries have emerged as an improvement to classic flow technology. Rather than storing energy in solution, redox -targeting flow batteries store energy in an insoluble solid while a solubilized electrolyte serves to shuttle electrons from the electrochemical cell to the solid. This strategy serves to combine the high energy density of solid-state batteries and scalability of flow batteries. Current redox targeting technology is mainly limited to the use of inorganic solid materials. These materials are cycle by an intercalation mechanism, which requires low current densities that lead to long cycle times. Furthermore, pairing shuttles with these materials are difficult because of distinct redox potentials and electron transfer rates of these solids. Our efforts focused on the development of an all-organic redox targeting flow battery. Organic materials generally do not operate based on intercalation mechanisms and the synthetic flexibility of organic compounds allow for the fin (open full item for complete abstract)

Committee: Christo Sevov (Advisor); Yiying Wu (Committee Member); Jovica Badjic (Committee Member) Subjects: Chemistry; Energy

Doctor of Philosophy, Case Western Reserve University, 2019, EMC - Mechanical Engineering

Redox flow batteries with flow field designs have been demonstrated to boost their capacities to deliver high current density in medium and large-scale energy storage applications. Nevertheless, the fundamental mechanisms involved with improved current density in flow batteries with serpentine flow field designs have been not fully understood. In this dissertation work, one-dimensional (1D) analytical model, two-dimensional (2D) numerical model with scaling analysis, and three-dimensional (3D) model of a serpentine flow field over the porous carbon paper electrodes have been developed to examine the distributions and amounts of pressure driven electrolyte flow penetrations into the porous carbon paper electrodes. It was found that the electrolyte flow penetrations are strongly under-estimated by 1D analytical model and 2D numerical model. The scaling analysis also demonstrates that the flow penetrations enhanced by the adjacent flow channels are significant, and were not able to be incorporated in the 1D and 2D models. The 3D model accounts the effects of landings/ribs bridged between the adjacent flow channels on flow penetrations and better calculates the amount of flow penetrations into the porous carbon paper electrodes. It was also found that the flow penetrations are sensitive to the properties of the porous electrode, i.e. permeability and porosity, a smaller permeability or porosity results in a much smaller flow penetration. The model is used to estimate the maximum current densities associated with the stoichiometric availability of electrolyte reactant flow penetrations through the porous carbon paper electrodes. The modeling results match reasonably well observed experimental data without using any adjustable parameters. This fundamental work on electrolyte flow distributions of limiting reactant availability will contribute to a better understanding of limits on electrochemical performance in flow batteries with serpentine flow field designs and should (open full item for complete abstract)

Committee: Robert Savinell (Advisor); Joseph Prahl (Advisor); Jesse Wainright (Advisor); Paul Barnhart (Committee Chair); Sunniva Collins (Committee Member); James T'ien (Committee Member) Subjects: Applied Mathematics; Chemical Engineering; Energy; Fluid Dynamics; Mechanical Engineering; Physics

Master of Sciences (Engineering), Case Western Reserve University, 2014, EMC - Mechanical Engineering

A macroscopic model of flow in a redox flow battery is developed. The model is a layered system comprised of a single passage of a serpentine flow channel and a parallel underlying porous electrode (or porous layer). As the fluid moves away from the entrance of the flow channel, two distinct fully developed flow regime evolve in the channel and the underlying porous layer, respectively. The effects of the inlet volumetric flow rates, permeability of the porous layer, thickness of the flow channel and thickness of the porous layer on the nature of the mass flow in the porous layer are investigated. The results show that, for a Reynolds number of 91.5 with the ideal plug flow inlet condition, the average filtration velocity decreases by a factor of about two as the number of carbon fiber paper layers is increased from 1 to 7. Significantly, reactant flow convection is found to estimate a corresponding maximum current density 403mA cm-2 and 742mA cm-2, which compares favorably with experiments of ~400mA cm-2 and ~750mA cm-2, for a single layer and three layers of the carbon fiber paper.

Committee: Iwan Alexander (Advisor); Robert Savinell (Advisor); Joseph Prahl (Committee Member); Donald Feke (Committee Member) Subjects: Aerospace Engineering; Chemical Engineering; Energy; Mechanical Engineering

Doctor of Philosophy (PhD), Wright State University, 2024, Environmental Sciences PhD

N-heterocyclic carbenes (NHCs), a characteristic 5-membered ring structure, contain a carbene carbon and at least one nitrogen atom. The presence of nitrogen atoms in the cyclic structure has two effects on its electronic structure: it withdraws σ-electrons and donates π-electrons to the carbene carbon, significantly enhancing the electronic richness and stability of the carbene center. Incorporating heteroatoms like sulfur, oxygen, or phosphorus into the NHC framework has paved the way for advanced developments in their structural properties. The incorporation of additional aromatic ring/heteroatom into NHC offers novel pathways for functionalization, ultimately broadening its scope of potential applications. The primary goal of this research project is to investigate the synthesis of metal-free tetrathiafulvalene annulated benzimidazolium (TTF-BzIm) salts and their possible application in redox-flow batteries (RFB) to be more eco-friendly. Additionally, the project aims to explore the properties and applications of a novel trithiocarbonate (TTC) annulated benzimidazolium (BzIm) carbene and its metal complexation studies. The beginning stages of the project focus on finding an efficient synthesis route to prepare trithiocarbonate-annulated benzimidazole NHC precursors, and their structural confirmation will be carried out by various characterization techniques such as Nuclear Magnetic Resonance (NMR), High-resolution mass spectrometry (HR-Mass), Fourier-transform infrared spectroscopy (FT-IR). Further, this new class of NHC precursors is complexed with transition metals to study their electrochemical behavior using Cyclic voltammetry (CV) and donor property in the presence of trithiocarbonate NHC backbone. NHCs are valued in material fabrication due to their stable metal-carbene bonds and ability to facilitate electron transfer. These beneficial properties stem from their ease of synthesis, the availability of synthetically modified ligands for various catalytic (open full item for complete abstract)

Committee: Kuppuswamy Arumugam Ph.D. (Committee Chair); Steven R. Higgins Ph.D. (Committee Member); Jitendra Kumar Ph.D. (Committee Member); Amit Sharma Ph.D. (Committee Member); Ioana E. Pavel Ph.D. (Committee Member) Subjects: Chemistry; Environmental Science

Doctor of Philosophy, University of Akron, 2024, Chemistry

Electrochemical methods, which collect data on potential and/or current, are useful techniques that have been utilized in various fields, including energy storage, medicine, and biology. My PhD research employs electrochemical methods in three areas: investigating redox flow batteries (RFBs), understanding heterogeneous electron transfer (ET) theories, and establishing a connection with machine learning (ML). This dissertation is organized into three parts accordingly. The first part of this dissertation (Chapters II through V) is the investigation of ferrocene-based aqueous redox flow batteries (ARFBs). The development of RFBs has gained significant attention in recent years due to the growing demand for efficient and reliable energy storage systems. ARFBs, which use water-soluble compounds, have become increasingly popular because of their lower electrolyte resistance, reduced cost, enhanced safety, and lower environmental impact. Ferrocene (Fc), which can be modified to be soluble in water, possesses a high reversibility and electron transfer rate, making it an ideal candidate for ARFBs. During my Ph.D. period, several new water-soluble sulfonated Fc based ARFBs were characterized, including 1,1′-bis(sulfonate)ferrocene dianion disodium (1,1'-FcDS), ferrocene-1,1'-bis(sulfonate)ferrocene dianionic salts with varying imidazolium cations, pyridinium salts of the ferrocene bis(sulfonate) dianion (FcPyr), 3-((ferrocenyl)methyldimethylammonio)-1-propanesulfonate (Fc3), and 4-((ferrocen-yl)methyldimethylammonio)-1-butanesulfonate (Fc4). The suitable structures of Fc for ARFB applications have been revealed. The second part of this dissertation focuses on understanding heterogeneous electron transfer. Various electroanalytical techniques, including steady-state current, cyclic voltammetry (CV), and differential pulse voltammetry (DPV), were simulated in COMSOL Multiphysics, and the results are presented in Chapter VI. Chapter VII describes the ET processes in a non- (open full item for complete abstract)

Committee: Aliaksei Boika (Advisor); Christopher Ziegler (Committee Member); Chrys Wesdemiotis (Committee Member); Chunming Liu (Committee Member); Zhong-Hui Duan (Committee Member) Subjects: Chemistry; Computer Science; Education; Energy

PhD, University of Cincinnati, 2020, Engineering and Applied Science: Chemical Engineering

Zeolite membranes possess tremendous potentials for efficient molecular separation via size-exclusion effects. However, practical realizations of this great potential have been hindered by nonselective permeation through intercrystalline spaces and high resistance to intracrystalline diffusion in the conventional polycrystalline zeolite membranes. Zeolite nanosheets with nanometer-scale thickness and very large aspect ratios offer new opportunities to control crystal orientation and minimize thickness of zeolite-composite membranes for achieving enhanced selectivity and flux in molecular and ion separations. However, there is currently a lack of success in synthesizing zeolite nanosheets with low Si/Al ratios in the framework, which is desired for high-performance ion separations or proton-selective ion conduction in aqueous solutions. This dissertation presents studies on the synthesis of alumina containing zeolite nanosheets, formation of zeolite nanosheet laminated membranes (ZNLM), and mechanisms of mass transport in the ZNLM for important applications in high concentration brine desalination and ion separations in redox flow battery (RFB). A continuous hydrothermal crystallization method with a scheduled change of precursor composition has been established for the synthesis of ZSM-5 (i.e. Al-containing MFI type) zeolite nanosheets. ZSM-5 nanosheets with micrometer-scale lateral dimensions (1.5 – 4 µm) and nanometer thickness (~6.7 nm) in the preferred straight channel direction (i.e. b-orientation) have been achieved for the first time. The ZSM-5 nanosheets have been used to fabricate ultrathin (<500nm) laminated membranes on macroporous a-alumina substrates. This ultrathin b-oriented ZSM-5 ZNLM with high surface hydrophilicity has demonstrated significantly higher water flux than the pure-silica MFI zeolite (silicalite) ZNLM. It also showed extraordinary water flux combined with high salt rejection in pervaporation desalination for brines containing up to (open full item for complete abstract)

Committee: Junhang Dong Ph.D. (Committee Chair); Anastasios Angelopoulos Ph.D. (Committee Member); Jianbing Jiang Ph.D. (Committee Member); Vesselin Shanov Ph.D. (Committee Member); George Sorial Ph.D. (Committee Member) Subjects: Chemical Engineering

Master of Science, University of Akron, 2018, Polymer Science

Since the first redox-flow batteries (RFBs) were demonstrated in the 1940s [22], RFBs attracted attentions duet to their relatively high specific capacity, excellent cycle life and flexible layout [23]. Traditional RFBs were constructed by using inorganic redox materials such as Vanadium salt. The cost of those systems is usually expansive and the materials are toxic. The conjugated molecules represented another class of redox materials that can be produced with abundant nature sources and provide better capacity/cost ratio. However, the most challenge to achieve the desired organic redox-flow batteries (ORFBs) is to design and synthesize ideal organic redox molecules with high solubility, large electrochemical window and reversible redox cycles. In this research, we focused on exploring electro-active conjugated molecules with high solubility and redox stability in non-aqueous condition. Diketopyrrolopyrrole (DPP), phenanthridinone (PN), ferrocene and viologen based molecules were designed and synthesized, and their electrochemical characteristics were studied.

Committee: Yu Zhu (Advisor); Li Jia (Committee Member) Subjects: Energy; Organic Chemistry