UC Merced

Limited resources of fossil fuels and climate change left human beings with no choicebut 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. PEMFC is a multi-component system with all kinds of mass, heat, electron, and ion transport physics included in its operation. Diffusion through porous media, mainly when liquid water is generated at high current densities, is challenging. A porous carbon-based gas diffusion media (GDM) is in charge of reactant transfer to the catalyst layer to fulfill electrochemical reactions and electron generation. Precise control of the heterogeneous microstructure of the porous media is one of the major materials engineering challenges to enhance mass transport in the fuel cell. Two porous components in PEMFC with the most heterogeneous microstructures are built upon assembly of carbon or catalyst supported on carbon agglomerates. These components are the micro-porous layer (MPL) in the diffusion media and the catalyst layer. MPL and catalyst layers are fabricated by deposition of a thin film of their precursor slurry (ink), which is a complex fluid. Significant interactions occurring during the formulation, mixing, and deposition of the precursor materials dictate the final properties and microstructure of the porous structure. Regarding the catalyst layer, optimization of the microstructure through ink materials engineering could lead to more catalyst utilization. Hence, a lower amount of precious platinum (catalyst) is needed to reach a particular performance in the PEMFC. This study employs a bottom-up approach to study the microstructure of the carbon network formed in ink as a function formulation and its evolution during the high shear deposition process. Finally, the findings are correlated to the in-situ fuel cell performance and oxygen transport resistance of the components in the PEMFC. For MPL, optimum formulation parameters and novel porous media using additives are introduced. A new approach is used to elucidate interparticle interactions in catalyst ink from the simultaneous response of the structure to mechanical shear forces and small alternating current (AC) perturbation.