X-ray fluorescence nano-imaging of long-term operated solid oxide electrolysis cells

In this work, we investigate using nanoscale X-ray fluorescence spectroscopy the degradation processes of a cathode and an electrolyte supported cell, produced by two different suppliers, that have been long-term operated in electrolysis mode. High-resolution compositional analysis in combination with high lateral resolution are presented in the format of a 2D map with 50 nm resolution for Ni, Y, Ce, Gd, La, Sr, Co, Fe. We report on the different elements that are diffusing already during the sintering process as well as their evolution after long-term operation. In both type of cell, Co is the element that is highly segregating from the LSCF electrode during the electrochemical reaction. The CGO barrier does not prevent the diffusion of Sr in the electrolyte of the CSC cell while it does in the ESC cell. In addition, the contact layer between the hydrogen electrode and the electrolyte in the ESC cell seems to prevent the Ni depletion. A high concentration of gadolinium from the CGO layer is visible at the CGO/electrolyte interface on the oxygen electrode side as well as on the hydrogen electrode side in the ESC cell. The gadolinium concentration significantly increases during the cell operation to form a layer of a few micrometers.