Chandra Macauley1 Peter Felfer1

1, Friedrich Alexander University, Erlangen, , Germany

The performance of electrochemical devices such as fuel cells or electrolyzers is often dictated by material properties at interfaces. Both fuel cells and electrolyzers contain interfaces between Nafion, a proton conducting polymer film, and catalysts, and electrolytes. It is widely known that the structure and functional properties of Nafion change significantly with water content. To investigate the relevant interfaces between the Nafion, catalyst layers and gas diffusion layers, it is essential to conduct 3D characterization in the near-operando state. Using techniques developed to study biological materials, focused ion beam (FIB) tomography of hydrated fuel cell/electrolyzer components was conducted at cryogenic temperatures. A custom transfer arm was designed and built to exchange samples between a cryo-fixation station and a Quorum Technologies PP3005 cryo-stage in a FIB-SEM. The resulting 3D-reconstructions and their implications for improving the performance of electrochemical devices will be discussed.