Oxygen Ion Adsorption Studies on La10Si6O27 (001) Surface with DFT Calculation for SOFC Electrolyte

The apatite-type material La_10-xSi₆O_27-1.5x (LSO) has promising future as electrolyte in SOFC for its high ionic conductivity ^[1-3]. In this work, ab-initio calculation based on density functional theory (DFT) ^[4] has been used to investigate the oxygen ion adsorption mechanisms and energy at different sites on the LSO (001) surface. The oxygen ion migration channel can be predicted using the results of adsorption energies on various sites. The most stable adsorption is shown at the hollow between La and O (located away from O-Si Tetrahedron), thus it should be a candidate channel of oxygen ion migration. Furthermore, the electronic properties, including the Fermi energy level, bond strength and length, have been changed with the ion adsorption, and the electrons transition features were obtained by density of states analysis. The calculated results also imply that LSO could be employed as possible electrolyte material due to its low formation and migration energies for the oxygen ion.

Keywords: Apatite electrolyte, Ab initio calculations, DFT, SOFC, ion adsorption. 

Reference:
1. H. Yoshioka, Y. Nojiri, S. Tanase, Solid State Ionics 179 (2008) 2165-2169
2. Guangchao Yin, et al, Journal of Alloys and Compounds 586 (2014) 279–284
3. Susumu Nakayama, et al, Ceramics International 40 (2014) 1221–1224
4. T.Q. Nguyen et al. Applied Surface Science, 288 (2014) 244–250