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Environmental Systems (ES)

PhdD Dissertation Defense


"Understanding the Microstructure and Interaction
Between Nanoparticles and Polymers Through the
Study of Precursor Complex Fluid in a PEMFC"

Shirin Mehrazi
Environmental Systems
University of California, Merced


Shirin Mehrazi is a Ph.D. candidate in the
Department of Environmental Systems at
University of California Merced. She joined
Professor Abel Chuang’s group in 2018 and worked
on hydrogen fuel cell materials engineering. She
received her B.Sc. in Materials Engineering from
Shiraz University, Iran (2012), and her M.Sc. In
Materials Engineering with a minor in corrosion
engineering from University of Tehran, Iran
(2014). In 2016 She joined University of Akron,
Akron, OH as a research assistant in the Chemical
Engineering program.

Limited resources of fossil fuels and climate change left human beings with no choice but to seek alternate clean energy providers. Green hydrogen is one of the strong candidates toward electrification. Proton exchange membrane fuel cell (PEMFC) is a device that converts chemical energy stored in hydrogen to electricity with water and heat as the only byproducts. Enhancement of PEMFC efficiency via performance improvement is a critical pathway toward its vast commercialization. A PEMFC is a multi-component system with combined mass, heat, electron, and ion transport physics during operation. Two of the most important PEMFC components, responsible for mass transport and electrochemical reactions, are fabricated by deposition of a carbon-based complex fluid (ink). The porous microstructure formed upon the assembly of carbon agglomerates have a significant effect on mass transport in the microporous layer (MPL) and availability of active sites in the catalyst layer. Understanding and optimizing the porous structure is key to further fuel cell performance enhancement. This study employs a bottomup approach to investigate the microstructure of the carbon network formed in the ink as a function of its formulation and evolution during the high shear deposition process. The findings are correlated to the in-situ oxygen transport resistance measurement and fuel cell performance in the PEMFC. An optimum formulation as well as a novel design incorporating additives in the microporous layer are introduced. In addition, a newly developed characterization tool to study both mechanical and electrical properties of the carbon network is incorporated to unravel the interparticle interactions in the catalyst ink. The results from this study provide new insights into designing a more effective and durable multi-component porous structure in a PEMFC.

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