Event
Special MSE Seminar: Eugene A. Kotomin
Friday, October 30, 2009
10:00 a.m.
Room 2110, Chemical and Nuclear Engineering Bldg.
Joanne Kagle
301 405 5240
jkagle@umd.edu
please note the special time and location.
First Principles Modeling of Oxygen Incorporation Into Solid Oxide Fuel Cell Cathode
Presented by Dr. Eugene A. Kotomin
Max Planck Institute for Solid State Research, and
University of of Latvia
A study of oxygen incorporation from the gas phase into oxides is both of fundamental interest as a simplest chemical reaction and of applied interest for catalysis and electrochemical devices such as sensors and solid oxide fuel cell (SOFC) cathodes [1,2].
We present and discuss here the results of first principles DFT plane wave supercell calculations of the atomic and molecular oxygen adsorption and diffusion on the LaMnO3 (001) surface which serves as a model system for SOFC cathode materials [3]. The dissociative adsorption of O2 molecules is energetically favorable on surface Mn ions even on a defect-free surface.
We discuss optimal adsorption sites for oxygen, binding energies, electronic density redistribution as well as charge transfer. We compare also the migration energies for adsorbed O species and surface oxygen vacancies. First principles thermodynamics based on our calculations predicts that at typical SOFC operation temperatures (~1200 K) the MnO2 (001) surface with adsorbed O atoms is the most stable in a very wide range of oxygen gas pressures (above 10-2 atm). Based on these detailed calculations, we consider several possible scenarios for the oxygen incorporation into the cathode with a special attention to the rate determiming step [4] and to the kinetics of mutual approach of adsorbates and surface oxygen vacancies.
[1] R. Merkle, J. Maier, H.J.M. Bouwmeester, Angew. Chemie Int. Ed. 43, 5069 (2004)
[2] R. Merkle, J. Maier, Topics Catal. 38, 141 (2006).
[3] E.A. Kotomin, Y. A. Mastrikov, E. Heifets, J.Maier, PCCP 10, 4644 (2008)
[4] R. Merkle, Y. A. Mastrikov, E. Heifets, E. A. Kotomin, M. Kuklja, J. Maier, Proc. Int. Conf. On Fuel Cells, Vienna, 2009, submitted.
