Modelling of the oxygen electrode for Solid Oxide Cells: study of the reaction mechanism and impact of the degradation

An elementary kinetic model was developed to predict the electrochemical response of porous LSCF and LSCF-CGO oxygen electrodes used in Solid Oxide Cells (SOC). For this purpose, an integrated approach coupling (i) electrochemical testing, (ii) advanced 3D characterizations, and (iii) modeling was proposed. The microstructural properties extracted from the 3D electrodes volumes obtained by FIB-SEM tomography were implemented in the model as input parameters. The model was validated on a large set of experiments performed under different operating conditions by testing symmetrical cells in a three-electrode configuration. The reaction mechanism of both studied electrodes was thoroughly analyzed and the rate-determining steps for the electrodes have been identified. The LSCF model was also extended to simulate the cyclic voltammetry curves. The resulting simulations were compared with semi-analytical solutions to check the relevance of this simplified approach to assess the voltammetry response of porous LSCF electrodes. From the experimental point of view, long-term tests and post-test characterizations were performed at the electrode and complete cell levels as experimental evidences to support a proposed degradation mechanism for the LSCF demixing. In parallel, the experimental data for the validation of the micro model for the hydrogen electrode have been collected. A special effort have been paid to assemble a steam generator system capable to produce a stable flow over a large range of water partial pressure. Finally, a sensitivity analysis has been performed with the LSCF full elementary model to study the impact of LSCF decomposition on the electrode response.

Direction/co-direction : Jérôme LAURENCIN, Laurent DESSEMOND, Marie PETITJEAN

Composition du jury :

Nicolas BION CHARGE DE RECHERCHE HDR CNRS délégation Limousin Poitou-Charentes Rapporteur
Pierre-Marie GEFFROY DIRECTEUR DE RECHERCHE CNRS délégation Limousin Poitou-Charentes Rapporteur
Jean-Paul VIRICELLE DIRECTEUR DE RECHERCHE Ecole des Mines de Saint Etienne Examinateur
Elisabeth SIEBERT DIRECTEUR DE RECHERCHE CNRS délégation Alpes Examinateur