Interfacial Properties of Bilayer SOFC Electrolytes Via Scale Bridging Simulations

Abstract

There has been significant interest in the bilayer materials used as Solid Oxide Fuel Cell Oxides (SOFCs) electrolytes. Multiple studies have explored the two participating materials in bilayer electrolytes, individually. However, the interfaces formed by them remain largely unexplored due to their complex nature. In order to advance the fundamental science of bilayer electrolytes, in this work a multiscale modeling study of the interface formed in commonly used SOFC electrolyte- ‘Ceria (CeO2)/yttria-stabilized zirconia (YSZ)’, was conducted. First, a realistic YSZ/CeO2 interface model containing all the important microstructural features of the interface such as dislocations, point defects, and lattice strains was prepared by using classical molecular dynamics (MD) simulations. Then, density functional theory was implemented to analyze the electronic properties of the realistic YSZ/CeO2 interface model prepared by MD. It was found that, at the interface, the overall strain in CeO2 and YSZ is compressive and tensile, respectively, as expected; however, the local strain at the core of the dislocation is converse. At dislocations, CeO2 was found to have tensile strain whereas YSZ has compressive strain. The presence of tensile strain in CeO2 at the core of the dislocations might contribute to the formation of O vacancies and reduction of Ce4+ to Ce3+, as observed in experiments. Overall, this work for the first time integrates the classical and quantum simulations to prepare and analyze a realistic working-class YSZ/CeO2 interface, resulting in the long-sought explanation for the experimentally observed Ce reduction at the YSZ/CeO2 interface.1 Acknowledgments This work was supported in part by the International Institute for Carbon-Neutral Energy Research (I2CNER) sponsored by the World Premier International Research Center Initiative (WPI) and the JSPS Core-to-Core Program, A. Advanced Research Networks and Paul Scherrer Institut. The computations were performed by using Computational Science Research Center, Okazaki, Japan, and the HPC supercomputers at I2CNER, Kyushu University, Japan.