Regensburg 2019 – wissenschaftliches Programm
MM 22.1: Vortrag
Mittwoch, 3. April 2019, 10:15–10:30, H43
First-Principles Calculations of Charge States in Defective SOFC/SOEC Perovskite Materials — •Daniel Mutter1, Daniel F. Urban1, and Christian Elsässer1,2 — 1Fraunhofer IWM, Wöhlerstraße 11, 79108 Freiburg — 2Freiburger Materialforschungszentrum FMF, Stefan-Meier-Str. 21, 79104 Freiburg
Solid oxide fuel cells (SOFC) and solid oxide electrolyzer cells (SOEC), which transform chemical into electrical energy and vice versa, have the potential to make a significant contribution to the efforts of overcoming future problems of the energy economy. An optimal functionality of these devices requires a high catalytic activity at the electrodes. This strongly depends on point defect concentrations and on the capability of the material to allow for fast charge transfer reactions. Promising anode materials regarding these requirements are perovskite compounds (ABO3), where the transition-metal ion on the B site can adopt different oxidation states by accepting and releasing electrons during the oxygen reactions at the SOEC/SOFC surfaces. We present results of density functional theory GGA+U calculations for the changes in oxidation states of the transition metal ions Fe and Mn in LaFeO3 and LaxCa1−xMnO3 (0≤ x≤ 1), respectively, when point defects such as anionic and cationic vacancies are present near the metal ions. After identifying the dominant defect species, a Bader charge analysis was performed and partial electronic densities of states were derived. The latter are compared to electron energy-loss near-edge spectra (ELNES), which are sensitive to changes of the bonding environment and hence of the oxidation states of individual atoms.