The electronic structure and the oxygen adsorption at BaO terminated surface of GdBaCo2O5.5: A first principles study

The double perovskites GdBaCo2O5.5 (GBCO) is candidate cathode materials for application in intermediate temperature solid oxide fuel cells (IT-SOFCs), attributing to excellent electrical conduction properties and oxidation activity. The electronic structure and the oxygen adsorption at BaO terminated surface of GBCO are investigated using projector augmented-wave (PAW) method based on spin-polarized density functional theory (DFT) with the inclusion of on-site Coulomb interaction. The BaO-terminated surface is adopted according to recent experimental results that this termination is energetically favorable for the double perovskites GBCO. We predict that G-AFM configuration is the most stable structure. The calculated results of oxygen vacancy energy indicate that the lowest energy vacancy positions are in the GdO layers. Charge transfer for the adsorbed oxygen and the surface ions is also examined by Bader charge analysis. The oxygen vacancies can facilitate oxygen adsorption and catalyze the bond cleavage. The existence of oxygen vacancy strengthens surface activity by acting as an active site at the surface. These results at the atomic level can contribute to the detailed understanding of oxygen reduction reaction mechanism.