Introduction Deterioration of oxygen reduction reaction (ORR) kinetics in the cathode side can be a main limiting factor1 for the overall performance of solid oxide fuel cells (SOFCs) that are a promising sustainable energy conversion device. The A-site cation segregation on perovskite surfaces may decrease the rate of ORR. It is therefore necessary to elucidate the underlying mechanism of the cation segregation for designing the new cathodes with high reactivity and stability in ORR. Computational Methods Plane wave density functional theory (DFT) calculations using the Vienna ab initio simulation package (VASP) were performed for all total energy calculations.2 The Perdew-Burke-Emzerhof (PBE) based on the generalized gradient approximation (GGA) was employed. To cancel the self-interaction errors, the DFT+U method was considered.3 Results and Discussion This work highlighted the two types of cation segregation on the A-site using density functional theory (DFT) calculations: (1) dopant cation segregation on LaBO3 (B = Cr0.50Mn0.50, Mn, Fe, Co0.25Fe0.75, Co, and Ni) perovskite surfaces and (2) lattice cation (Sr) segregation on SrTi1-xFexO3 perovskite surfaces. From our DFT calculations, we demonstrated that minimization of elastic energy introduced by constituent A- and B-site cations plays an important role in surface segregation (Figure 1). Based on these results, design principles for suppressing the cation segregation were suggested. Especially, it was possible to predict good material candidates from only an ionic radii database. Conclusions Our results indicated that cation segregation phenomena on the perovskite surfaces can be effectively controlled by minimizing the elastic energy caused by constituent cations. References (1) Singhal, S. C.; Kendall, K. In High Temperature Solid Oxide Fuel Cells: Fundamentals, Design and Applications; Elsevier: Oxford, 2003. (2) Kresse, G.; Furthmüller J. Phys. Rev. B 1996, 54, 11169. (3) Dudarev, S. L.; Botton, G. A.; Savrasov, S. Y.; Humphreys, C. J.; Sutton, A.P. Phys. Rev. B 1998, 57, 1505

Suppressing cation segregation on perovskite surfaces to design high-performance cathode materials in solid oxide fuel cells

251st National Meeting (2016)

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