Understanding transport processes in electrochemical devices (fuel cells, electrolyzers and batteries) is critical for effective energy conversion and storage. Interfacial phenomena of charge and mass transfer depends on local species distribution and probing these interfaces remains a challenge. Tools that are designed for characterization of porous media on a larger scale are not always applicable for thin (&lt; 10 um) electrodes. Furthermore, nano- and micro-scale transport processes need to be bridged, as these electrodes are hierarchically structured. Fine nano-structures of carbon and other materials are desirable for high surface area and the features of a larger size are needed for higher mass and ion transport. Synchrotron X-ray computed tomography (CT) is well-fit to characterize transport in porous electrodes due to its fast, non-intrusive measurements and relatively high resolution. For polymer-electrolyte fuel cells (PEFCs) and anion exchange membrane fuel cells (AEMFCs) effective water management remains a hurdle. During start-up at lower temperatures liquid water formed as a byproduct of electrochemical reaction can block gas (reactant) delivery to a catalyst, resulting in flooding, mass-transport losses, and low cell power densities. Using synchrotron X-ray CT we have previously correlated electrode morphology and transport under various cell compression. These ex- and in-situ studies are useful and shed light on an isolated transport phenomena. Continuum, pore-network and direct meshing models complement the observed phenomena and guide the fuel cells components design. By introducing the capabilities for in-operando synchrotron X-ray CT water distribution under various operating condition became possible. This presentation focuses on in-operando techniques for understanding water management in PEFCs and AEMFCs and examples of various operating conditions will be presented. Furthermore, two more applications of X-ray CT will be presented: batteries characterization and water transport in electrolyzers.

Characterizing transport in electrochemical energy conversion devices with X-ray computed tomography

254th National Meeting (2017)

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