Engineering Commons^™

Electrode Development And Electrocatalysts Design For Polymer Electrolyte Membrane Fuel Cells, Xiong Peng

Theses and Dissertations

Because of environmental issues and national conflicts caused by overuse of fossil fuels, there is a need to seek renewable ways to utilize energy. In the transportation sector, hydrogen-based polymer electrolyte membrane fuel cells, including proton exchange membrane fuel cells (PEMFCs) and anion exchange membrane fuel cells (AEMFCs), have been considered as a promising alternative to conventional combustion engines. However, the widespread commercialization of both PEMFCs and AEMFCs has been hindered by several factors, including cost and performance. In this thesis, a series of topics including electrode fabrication, electrocatalyst development for both PEMFCs and AEMFCs, as well as the water …

Computational Modeling Of The Structure And Catalytic Behavior Of Graphene-Supported Pt And Ptru Nanoparticles, Raymond Gasper

Doctoral Dissertations

Computer modeling has the potential to revolutionize the search for new catalysts for specific applications primarily via high-throughput methodologies that allow researchers to scan through thousands or millions of potential catalysts in search of an optimal candidate. To date, the bulk of the literature on computational studies of heterogeneous catalysis has focused on idealized systems with near-perfect crystalline surfaces that are representative of macroscopic catalysts. Advancing the frontier to nanoscale catalysis, in particular, heterogeneous catalysis on nanoclusters, requires consideration of low-symmetry nanoparticles with realistic structures including the attendant complexity arising from under-coordination of catalyst atoms and dynamic fluxionality of clusters. …

Effects Of Air And Other Gases In The Stabilization Process Of The Superprotonic Phase Of Cesium Dihydrogen Phosphate Within A Hermetically Sealed Chamber, Israel Martinez

Open Access Theses & Dissertations

The solid acid CsH2PO4 (CDP), exhibits a sudden increase in its proton conductivity as it’s heated above a certain temperature (around T~235oC), which makes it a very attractive candidate to be used as an electrolyte in intermediate temperature fuel cells. Unfortunately, at these temperatures the sample is not stable, as starts to dehydrate; which causes a dramatic drop in the proton conductivity over a short period of time (less than one hour). In order to inhibit, or at least delay, the dehydration process, the solid acid it’s put under a saturated water vapor atmosphere. Another method to stabilize the highly …

Fundamentals Of Srcoo3 Based Oxygen-Deficient Perovskites As Cathodes For Solid Oxide Fuel Cells, Tianrang Yang

Theses and Dissertations

The local structure and oxygen stoichiometry in oxide systems have a profound impact on oxygen electrocatalysis encountered in metal-air batteries and solid oxide fuel cells (SOFCs). However, this knowledge is often obtained under conditions different from the real working conditions of the material, resulting in misinterpretation and misunderstanding. This PhD dissertation aims to obtain the structure and oxygen stoichiometry information of a class of perovskite oxides under their real working conditions in solid oxide fuel cells. Several perovskite oxides were selected for the study: Sr0.9Y0.1CoO3- (SYC10), Sr0.9Y0.3CoO3- (SYC30), SrCo0.9Nb0.1O3- (SCN10) and SrCo0.9Ta0.1O3- (SCT10). The local crystal structure and oxygen stoichiometry …

Multiscale Modeling Approach To Understand Active Sites In Non-Conventional Catalyst Layers For Fuel Cell Applications, Diana Constanza Orozco Gallo

Doctoral Dissertations

Fuel cells development required stable, active and more abundant catalytic materials. Oxygen reduction reaction (ORR) is the key process to enhance better activity and reduce the fabrication costs. Pt-based has proven to be the best catalyst for ORR and greater efforts has been made in terms of reducing the Pt content in the electrodes, reduce electrode thickness and enhance better catalytic activities. To overcome many of the challenges present, the catalyst layer studies are the great importance in the fuel cell community. Understanding catalyst layer with new catalytic materials, and configurations requires the development of methodological approach to relate structure, …

Structural, Interfacial, And Electrochemical Properties Of Pr2nio4+Δ – Based Electrodes For Solid Oxide Fuel Cells, Emir Dogdibegovic

Theses and Dissertations

Currently, the electrochemical performance and performance durability of solid oxide fuel cells (SOFCs) are limited by cathode materials. The high polarization resistance and phase instability of the cathode are two major challenges to hinder the commercialization of SOFC systems. Two families of oxides are presently known as potential cathode materials for SOFCs: (1) the perovskite family of oxides with a general formula of ABO₃, and (2) the Ruddlesden-Popper (RP) family of oxides (e.g. nickelates) with a general formula of A₂BO₄. The electron-hole conduction in these materials occurs simultaneously with oxygen ion conduction based on …

Polymer And Small Molecule Designs For Anion Conducting Membranes: Connected Ion-Channel Morphologies And Highly Alkaline Stable Ammonium Cations, Sedef P. Ertem

Doctoral Dissertations

Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE …

Optimization Of Titanium Liquid/Gas Diffusion Layers In Proton Exchange Membrane Electrolyzer Cells, Stuart Mccoy Steen

Masters Theses

Polymer electrolyte membrane electrolyzer cells (PEMECs), which are reverse PEM fuel cells (PEMFCs), are effective energy storage medium by producing hydrogen/oxygen from water using electricity from renewable energy sources. This is due in part because of its efficiency, high energy density, compact design, and large capacity. In a PEMEC, a liquid/gas diffusion layer (LGDL) is located between the catalyst layer and the current distributing flow field. The LGDL is expected to transport electrons, heat, and reactants/products to and from the catalyst layer with minimum voltage, current, thermal, interfacial, and fluidic losses. Carbon materials (carbon paper or carbon cloth), typically used …

Study And Development Of Sulfated Zirconia Based Proton Exchange Fuel Cell Membranes, Brittany Wilson Kemp

Doctoral Dissertations

With the increasing consumption of energy, fuel cells are among the most promising alternatives to fossil fuels, provided some technical challenges are overcome. Proton exchange membrane fuel cells (PEMFCs) have been investigated and improvements have been made, but the problem with Nafion®, the main membrane for PEMFCs, has not been solved. Nafion® restricts the membranes from operating at higher temperatures, thus preventing them from working in small electronics. The problem is to develop a novel fuel cell membrane that performs comparably to Nafion® in PEMFCs.

The membranes were fabricated by applying sulfated zirconia, via template wetting, to porous alumina membranes. …

Dynamic Simulation Of Turbine Engine Used With Molten Carbonate Fuel Cell For Power Generation In The Megawatt Range, Carlos Eduardo Gutierrez

Browse all Theses and Dissertations

Molten carbonate fuel cells (MCFC) have a high operating temperature of approximately 650° C (1200° F) to achieve sufficient conductivity of its carbonate electrolyte. Therefore, a gas turbine engine coupled with a MCFC is desirable since the turbine engine can be used to provide hot gas to the cathode, and the cathode gas residue can be used to raise the temperature of the natural gas and water vapor mixture (fuel) before it enters the MCFC at the anode. Dynamic models of a hybrid power plant consisting of a gas turbine engine and a MCFC with their respective components were developed …

Ion Mobility Studies Of Functional Polymeric Materials For Fuel Cells And Lithium Ion Batteries, Shilpi Sanghi

Open Access Dissertations

The research presented in this thesis focuses on developing new functional polymeric materials that can conduct ions, H⁺, or OH^- or Li⁺. The motivation behind this work was to understand the similarities and/or differences in the structure property relationships between polymer membranes and the conductivity of H⁺ and OH^- ions, and between polymer membranes and the anhydrous conductivity of H⁺ and Li⁺ ions. This understanding is critical to developing durable polymer membranes with high H⁺, OH^- and Li⁺ ion conductivity for proton exchange membrane fuel cells (PEMFCs), …

On Developing Novel Energy-Relates Nanostructured Materials By Atomic Layer Deposition, Xiangbo Meng

Electronic Thesis and Dissertation Repository

ABSTRACT

This thesis presents the fabrication of a series of novel nanostructured materials using atomic layer deposition (ALD). In contrast to traditional methods including chemical vapor deposition (CVD), physical vapor deposition (PVD), and solution-based processes, ALD benefits the synthesis processes of nanostructures with many unrivalled advantages such as atomic-scale control, low temperature, excellent uniformity and conformality. Depending on the employed precursors, substrates, and temperatures, the ALD processes exhibited different characteristics. In particular, ALD has capabilities in fine-tuning compositions and structural phases. In return, the synthesis and the resultant nanostructured materials show many novelties.

This thesis covers ALD processes of four …

A Systems Engineering Reference Model For Fuel Cell Power Systems Development, T. L. Blanchard

ETD Archive

This research was done because today the Fuel Cell (FC) Industry is still in its infancy in spite over one-hundred years of development has transpired. Although hundreds of fuel cell developers, globally have been spawned, in the last ten to twenty years, only a very few are left struggling with their New Product Development (NPD). The entrepreneurs of this type of disruptive technology, as a whole, do not have a systems engineering 'roadmap", or template, which could guide FC technology based power system development efforts to address a more environmentally friendly power generation. Hence their probability of achieving successful commercialization …

Composite Membranes For Proton Exchange Membrane Fuel Cells, Jinjun Shi

Browse all Theses and Dissertations

Proton exchange membrane fuel cells (PEMFCs), often regarded as a green energy source, have become a promising candidate to replace traditional power sources. One of the obstacles toward commercialization of PEM fuel cells is lack of high performance and low cost proton exchange membranes. The objective of this study was to develop and evaluate higher-performance, Nafion-based composite proton exchange membranes that are suitable for operating at higher temperatures (> 85°C).

Proton exchange membranes were prepared by adding silica and heteropolyacids (HPAs) to a proton-conducting polymer matrix, Nafion. The added silica powder particles, either by direct mixing or sol-gel reaction, were …

An Investigation Into Fuel Cells And Flow Cytometers Optimal Design, Etim Sunday Udoetok

LSU Doctoral Dissertations

The aim of the fuel cells part of this project was to investigate the performance of Proton Exchange Membrane Fuel Cells and closely related fuel cell types like the Alkaline Fuel Cells and Phosphoric Acid Fuel Cells. The investigation involved understanding the performance of fuel cells, addressing the shortcomings of currently used designs, and finding new methods for improving the performance of fuel cells. CFD was used to study flow channels and information learned from the study was used to design a new and improved flow channel. A prototype of the new design was fabricated, tested and found to perform …

The Biochemical Fuel Cell : Conversion Of Waste To Energy, Charles August Mielke

Theses

A batch biochemical-fuel cell was constructed and studies on the production of bioelectric energy using an alga Scenesdesmus quadricauda, and a bacterium Desulfovibrio desulfuricans, were conducted. Results were compared for a steady state cell using various concentrations of media components and showed that a 1000-fold increase in the concentration of media components produced a net potential output of 0.03mv/ml compared to an initial output of 0.02mv/ml. Further studies showed the biochemical net potential output using activated sludge from a waste treatment facility was 0.01mv/ml compared to 0.02mv/ml for the cell using the initial media concentration.

The system exhibited steady state …