Date of Award

8-16-2024

Document Type

Open Access Dissertation

Department

Chemical Engineering

First Advisor

Sirivatch Shimpalee

Second Advisor

John Regalbuto

Abstract

Alternative power generation has grown significantly in the space of energy production over the last ten years. Development of new technologies to produce energy is vital to the growing need for electricity. Batteries, solar panels, wind turbines, and countless other renewable energy options have been deemed necessary to create an overall greener future. Fuels cells when combined with electrolyzer show a promising system for stationary power generation. Both technologies are comprised of multiple parts in contact that must work together simultaneously to create an ideal environment for catalytic reactions to take place. A crucial component to a properly functioning cell is the porous media that is in contact with the catalyst layer. Specifically, the gas diffusion layer for fuel cells and porous transport layer for electrolyzers. The focus of this work is to observe the influence of different pore structures on transport phenomena to determine the best physical properties of the porous media for the desired application.

First, liquid transport through different gas diffusion layers, with and without a microporous layer, was studied. Inside a fuel cell, the gas diffusion layer is responsible for transporting fuel to the catalyst layer and maintaining saturation to aid the chemical reaction. Simulations of liquid evolution from gas diffusion layers, without a microporous layer, showed saturation peaks around the inlet positions. Liquid traveled vertically and did not distribute across the entire sample. When adding a microporous layer to the gas diffusion layer, full saturation across the sample was observed. Second, a multiscale simulation approach was taken to determine the best porous transport layer geometry for simultaneous two-phase transport. A microscale model was used to simulate oxygen evolution through different single and bilayer porous transport layers was simulated. Inside a proton exchange membrane water electrolyzer, oxygen is produced on the anode side of the cell. The porous transport layer’s main function is to remove oxygen from the catalyst surface. Oxygen evolution is dependent on capillary pressure. This means oxygen must fill a pore completely before entering the next pore. Single layer porous transport layers resulted in transport pathways combining into one layer pathway until exiting the sample. To improve the transport behavior, a second layer was added to create a bilayer porous transport layer. The first layer was a sinter powder material with smaller pore sizes. The second layer was a sinter fiber material that had large pore sizes compared to the first layer. Implementing a bilayer geometry resulted in multiple pathways and more oxygen being removed from the surface. Results from the micro scale simulation were used to inform a macroscale model of a standard lab scale Proton Exchange Membrane Electrolyzer to predict performance for each porous transport layer geometry.

Rights

© 2024, Mitchell Sepe

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