Specifically, micro-CT cannot capture the MPL nanopores, while its field of view is restricted to 2–3 gas channels at best 24, 25, 26. However, the current resolution and field of view of micro-CT is not able to fully resolve a PEMFC porous structure 3. In synchrotron facilities, operando imaging of PEMFCs can be captured in less than 20 s using micro-CT to capture the liquid water through the MPL and/or GDL pores 2, 17, 18, 21, 22, 23. Of these techniques, X-ray micro-computed tomography (micro-CT) offers the highest spatial resolution (0.5–3 μm), and field of view (1– 6 mm based on a 2000 2 pixel detector) 20. Several operando water visualisation methods have emerged in PEMFCs such as optical imaging (requiring an opened flow field or transport window), neutron imaging with low spatial and temporal resolution, X-ray radiography (low spatial resolution), and X-ray micro-computed tomography (micro-CT) 14, 15, 16, 17, 18, 19. Observing PEMFC water transport and diffusion with high levels of detail is essential to studying these spatial variations in porous structure and improving PEMFC designs. This “dual-porosity” flow between MPL/GDL pores and perforations and cracks is well-known for multiphase flow through heterogeneous and fractured porous media such as rocks 12, 13, and is critical to optimise PEMFCs multi-phase flow dynamics. These features create stable and interconnected water channels inside the electrode, reducing MPL and GDL water content and improving the gas and water balance. Most notably, large perforations and cracks in the MPL and GDL, initially regarded as manufacturing defects, significantly ease water diffusion from the catalyst layer 10, 11. Water management in PEMFCs has been improved by modifying the MPL and GDL properties 2, 9. Thus, a trade-off between flooding and dehydration is crucial for high-performing PEMFCs 6, 7, 8. If not sufficiently removed, liquid water will eventually accumulate in the GDL and MPL, challenging gas diffusion to the active sites and thereby flooding the PEMFC. At high loads, the generated water may saturate the moisture carrying capacity of the oxygen (air) and condense into droplets in the porous media 2. The performance of PEMFCs is highly dependent on the diffusion and utilisation of the fuel and oxidant gases at the anode and cathode, and on the efficient management of the water generated at the cathode 4, 5. This multilayered architecture both maximises gas diffusion to the active catalytic sites and minimizes water accumulation in the catalyst layers 3. PEMFCs are a multi-scale porous media comprising of a solid electrolyte membrane sandwiched between nanoporous electrocatalyst on both sides, covered by a microporous layer (MPL), a microporous gas diffusion layer (GDL), and topped by millimetre-scale flow channels (Fig. They electrochemically convert hydrogen into protons and electrons at the anode, which react with oxygen at the cathode to generate electricity with water as the only by-product. PEMFCs, consuming hydrogen and oxygen to generate electricity and water, offer the advantages of a low operating temperature (<80 oC), high-energy density and quick refuelling 2. Hydrogen fuel cells, and proton exchange membrane fuel cells (PEMFCs) in particular, are key to this green revolution due to their high energy conversion efficiency and zero-emission operations 1. This generalisable approach unveils multi-scale water clustering and transport mechanisms over large dry and flooded areas in the gas diffusion layer and flow fields, paving the way for next generation proton exchange membrane fuel cells with optimised structures and wettabilities.Ĭlimate change has shifted the focus from fossil fuels towards clean and renewable energy sources, with the hydrogen economy emerging as a worldwide solution. The resulting image is the most resolved domain (16 mm 2 with 700 nm voxel resolution) and the largest direct multi-phase flow simulation of a fuel cell. Herein, an advancement in water modelling is achieved using X-ray micro-computed tomography, deep learned super-resolution, multi-label segmentation, and direct multi-phase simulation. In addition, currently inadequate imaging and modelling capabilities are limiting simulations to small areas (<1 mm 2) or simplified architectures. Accurate liquid water modelling is inherently challenging due to the multi-phase, multi-component, reactive dynamics within multi-scale, multi-layered porous media. Proton exchange membrane fuel cells, consuming hydrogen and oxygen to generate clean electricity and water, suffer acute liquid water challenges.
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