Introduction Elemental analysis using energy-dispersive X-ray fluorescence (XRF) is a common practice is many different disciplines and fields [1]. In electrochemical systems such as Solid Oxide Cells (SOC), XRF is often used, in conjunction to other imaging techniques (TEM, FIB-SEM, X-ray CT), to ex-situ analyze the electrodes microstructural and composition evolution consequent to diverse degradation phenomena. Anode sulphur poisoning [2,3], cathode chromium poisoning [4], and interconnect corrosion [5] are just some examples. In this study, we propose to use a combination of XRF spectra analysis, elemental maps distributions and numerical models to predict the most probable degradation phenomena that affected the cell during operation. We investigate the beginning-of-life and the end-of-life XRF measurements to build a predictive numerical model that discerns between a combination of the following major microstructural physical and chemical degradation phenomena: i) Ni coarsening and oxidation; ii) Ni evaporation/migration; iii) increased porosity; iv) cathode Cr poisoning. Experimental methods We test a set of 9 anode-supported disc-shaped SOCs. Each cell is characterized by a diameter of 74 mm (active area equals 43 cm2). The anode is comprised of a 400 μm (of which approximately 390 μm constitute the support porous layer) NiO-YSZ cermet and the cathode is a 12 μm LSC layer. Electrolyte is 4.5 μm YSZ non-porous layer. We test each cell with H2/N2/H2O mixtures in a Greenlight G15-1030 X100 test stand connected to a Gamry 5000 potentiostat. Once the cells reach their end-of-life condition, either due to increased long-term degradation or failure, an Horiba XGT-7200 analytical microscope performs post-mortem analysis using XRF spectroscopy. Numerical methods We propose the development of numerical model to analyze the elemental map distributions of 7 atomic species (Ni, Y, Zr, La, Sr, Co, Cr) and the XRF spectra response to identify the most probable degradation phenomena amongst those listed. Discussion Figure 1 shows the elemental map of Nickel for two anodes. The top left map shows an anode that reached its end-of-life condition due to a short-circuit in the experimental setup, but it did not suffer any microstructural degradation and was brought to ambient temperature at a reduced state. In the top right map, the anode suffered Nickel oxidation due to air crossover caused by a thermo-mechanically induced crack. It is noticeable how the intensity and distribution of the Ni map in the oxidized anode response is faded compared to the fully reduced cell. Moreover, the XRF spectrum shows the presence of other elements (La, Sr, Cr, Co) suggesting: i) a variation in the morphological structure of the anode that allows the identification of cathodic elements from an “anodic view”, and; ii) the combined electrode degradation due to Cr poisoning.[1] M. West, A. T. Ellis, P. J. Potts, C. Streli, C. Vanhoof, P. Wobrauschek, J. Anal. At. Spectrom. 2015, 30, 1839–1889.[2] M. Riegraf, A. Zekri, M. Knipper, R. Costa, G. Schiller, K. A. Friedrich, J. Power Sources 2018, 380, 26–36.[3] W. M. Harris, J. J. Lombardo, G. J. Nelson, B. Lai, S. Wang, J. Vila-Comamala, M. Liu, M. Liu, W. K. S. Chiu, Sci. Rep. 2015, 4, 5246.[4] N. H. Menzler, I. Vinke, H. Lippert, ECS Trans. 2019, 25, 2899–2908.[5] J. Puranen, M. Pihlatie, J. Lagerbom, G. Bolelli, J. Laakso, L. Hyvärinen, M. Kylmälahti, O. Himanen, J. Kiviaho, L. Lusvarghi, et al., Int. J. Hydrogen Energy 2014, 39, 17284–17294. Figure 1