Can Hydrologists Study Fuel Cells?

Presenter: Wenqian Zhang1
Co-Author(s): Sidian Chen
Advisor(s): Dr. Bo Guo
1Department of Hydrology and Atmospheric Sciences, University of Arizona

Panapto Presentation Video
Poster PDF
Poster Session 2

Proton exchange membrane fuel cells (PEMFCs) are energy conversion devices that convert the chemical energy of hydrogen and oxygen to electricity. With essentially zero carbon emissions, fuel cells are expected to play a vital role in a low-carbon economy in the future. But, what do fuel cells have to do with hydrologists? You may be surprised by how similar the physical and chemical processes in fuel cells are to the water and species transport in soils and rocks that we study as hydrologists. Here is how a fuel cell system works. For the hydrogen and oxygen to continuously react and generate electricity, a fuel cell system is often designed so that the oxygen needs to diffuse through a so-called gas diffusion layer (GDL) and a microporous layer (MPL) to reach the catalyst layer. The oxygen then reacts with the proton with the help of chemical catalysts. This process generates electricity, but it also generates a byproduct—liquid water. The generated liquid water needs to be drained through the MPL-GDL in the counter direction for a fuel cell system to be sustainable—water flooding can impede the transport of oxygen. Therefore, efficient water management in the MPL-GDL double layer is critical for running fuel cell systems. However, the microscale processes of water transport in the porous layers remains poorly understood and the lack of fundamental understanding poses significant challenges for better engineering fuel cells. To address this critical knowledge gap, we develop a pore-network model to understand liquid water percolation in the MPL-GDL double layer. A stochastically-generated dual-scale pore-network is used to represent the MPL-GDL system. We then develop an invasion percolation algorithm to simulate the capillary flow. Our preliminary simulations show that the new pore-network model can effectively represent th water transport processes in the MPL-GDL system and provide water transport fluxes that are consistent with experimental observations.

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