Case Study: Spatially-resolved chemical imaging of an industrially-relevant hydrogen PEM fuel cell under operating conditions
Finden Ltd, ESRF, Université Grenoble Alpes, University of British Columbia
Techniques that can simultaneously probe all the components of functional devices at the nanoscale are urgently required to optimize the MEA architecture and operating conditions. Spectromicroscopy approaches using electron, neutron, and photon beams are powerful but generally laborious and/or limited to ex situ experiments. Significant advances in spatial and time resolution with in situ X-ray absorption tomography have been recently achieved. However, spatial resolution is often limited to scales greater than 100 nm and lacks the critical nanoscale and chemical information about the catalyst and supporting materials. This information is necessary to connect the catalyst activity, morphology, and stability to the overall MEA performance. These properties determine the device’s life cycle, with a major impact on its economic feasibility.
Hydrogen PEM fuel cell
We studied the catalyst degradation phenomena in an operating PEMFC using novel high-energy X-ray scattering techniques, simultaneously mapping the chemical composition with X-ray diffraction computed tomography (XRD-CT) and the nanostructure by small-angle X-ray scattering computed tomography (SAXS-CT) across the device scale of several centimeters. The proliferation of hydrogen fuel cell systems is hindered by a degradation of the platinum catalyst. We provided a device-level assessment of the catalyst degradation phenomena and its coupling to nanoscale hydration gradients, using advanced operando X-ray scattering tomography tailored for device-scale imaging. Gradients formed inside the fuel cell produce a heterogeneous degradation of the catalyst nanostructure, which can be linked to the flow field design and water distribution in the cell.
Striking differences in catalyst degradation are observed between operating fuel cell devices and the liquid cell routinely used for catalyst stability studies, highlighting the crucial impact of the complex operating environment on the catalyst degradation phenomena. This degradation knowledge gap accentuates the necessity of multimodal, in situ characterization of real devices when assessing the performance and durability of electrocatalysts and, more generally, electrochemically active phases used in energy conversion and storage technologies.
Imaging Heterogeneous Electrocatalyst Stability and Decoupling Degradation Mechanisms in Operating Hydrogen Fuel Cells. Martens I., Vamvakeros A., Martinez N., Chattot R., Pusa J., Blanco M.V., Fisher E.A., Asset T., Escribano S., Micoud F., Starr T., Coelho A.A., Honkimäki V., Bizzotto D., Wilkinson D.P., Jacques S.D.M., Maillard F., Dubau L., Lyonnard S., Morin A., Drnec J., ACS Energy Letters, 6 (8), 2021, DOI: https://doi.org/10.1021/acsenergylett.1c00718