Understanding transport processes in thin and porous materials is critical for electrochemical energy applications. Tools that are designed for material characterization on a large scale are not always applicable for thin (< 500 um) layers and films. Specific care needs to be taken to design hardware to observe transport phenomena on micro- and nano-scales. To correlate transport and morphology on these minute length and time-scales synchrotron X-ray computed tomography (CT) is well fit due to its fast, non-intrusive measurements, bright energy sources and relatively large field-of-view to spatial resolution ratios ^{1, 2}.

Water management is critical for polymer-electrolyte fuel cells (PEFCs), anion exchange membrane fuel cells (AEMFCs) and polymer electrolyte membrane (PEM) electrolyzers, as depending on a device, water is used as either a reactant or byproduct of electrochemical reaction and its location, as well as transport is critical for these devices operation. In PEFCs during start-up and operation 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. For AEMFCs water is a reactant in the cathode and its transport from the anode is critical for the cell operation. Addressing and understanding water transport issues, is made possible by introducing the capabilities for in-operando X-ray CT. In this presentation a single serpentine channel, 1 cm² active area fuel cell and electrolyzer operating at 30 and 60^oC will be presented. Cells with Platinum-group medals (PGM) and PGM-free electrodes on either cathode or anode will be presented with examples of water distributions. It was observed that for PGM-free electrodes water accumulates at components interfaces, where large voids are present. For electrolyzers water distribution in the anode under 50 and 200 mA/cm²will be shown. Furthermore, application of nano- X-ray CT for in-operando PEFCs will be demonstrated, as well as micro-CT for in-situ batteries characterization.

References

1. I. V. Zenyuk, A. Lamibrac, J. J. Eller, D. Y. Parkinson, F. Marone, F. N. Büchi and A. Z. Weber, The Journal of Physical Chemistry C, 2016.

2. I. V. Zenyuk, D. Y. Parkinson, G. Hwang and A. Z. Weber, Electrochemistry Communications, 2015, 53, 24-28.