X-ray Computed Tomography Visualization of Liquid Water in Proton Exchange Membrane Fuel Cells: A State-of-the-Art Review

Liquid water visualization in an operating fuel cell is a sophisticated research field that integrates interdisciplinary expertise in engineering, physics, optics, chemistry, materials science, imaging, image processing, and computational modeling. Advances in visualization techniques, such as X-ray computed tomography (XCT), have enabled observations of water transport and distribution inside proton exchange membrane fuel cells (PEMFCs) under in situ/operando conditions. Combined with electrochemical characterization and modeling tools, this approach can improve our understanding of the fundamental mechanisms of the dynamic water behavior and their impact on the cell performance and durability based on the structure–property–function relationships within the PEMFC core components. This article presents a concise review of the state-of-the-art literature featuring XCT methodology for water visualization in PEMFCs, including the flow field and all parts of the membrane electrode assembly. It synthesizes the key current trends and highlights the challenges and future research opportunities in the field, contributing to the development of high-power-density, durable, and cost-effective PEMFC technology.