Manfred Martin
RWTH Aachen University, Germany
Title: Oxygen ion conducting materials for energy conversion in fuel cells and batteries
Biography
Biography: Manfred Martin
Abstract
Interest in materials exhibiting oxygen ion conduction has increased owing to their great importance for energy conversion in Solid Oxide Fuel Cells (SOFC), Solid Oxide Electrolyser Cells (SOEC) and Rechargeable Oxide Batteries (ROB). Ceria-based oxides are regarded as key oxide materials because rare earth-doped ceria shows high oxygen ion conductivity even at intermediate temperatures. Using Density-Functional Theory (DFT), we have investigated defect formation and migration energies as well. Using Kinetic Monte Carlo (KMC) simulations, we then investigated the oxygen ion conductivity. We show that all interactions between the defects, namely vacancy-dopant attraction, dopant-dopant repulsion and vacancy-vacancy repulsion contribute to the so-called conductivity maximum of the ionic conductivity. Solid oxide electrolyser cells based on yttria-doped zirconia as electrolyte were operated for 6100 h and 9000 h, respectively. They were analyzed concerning degradation by various electron microscopy as well as micro-analytical techniques. We found several degradation phenomena such as formation of nano-sized pores at grain boundaries, formation of SrZrO3 at the interface electrolyte/anode and agglomeration of nickel particles in the cathode. The origin of these degradation phenomena is discussed in terms of the mass transport processes in the electrolyte caused by the two applied driving forces, namely the electrical potential and the oxygen potential gradient. Finally the new concept of Rechargeable Oxide Batteries (ROB) will be discussed.
Recent Publications:
1. Grope B, Zacherle T, Nakajama M, Martin M (2012) Oxygen ion conductivity of doped ceria: a Kinetic Monte Carlo study. Solid State Ionics 225:476-483.
2. Grieshammer S, Grope B, Koettgen J, Martin M (2014) A combined DFT + U and Monte Carlo study on rare earth doped ceria, Phys. Chem. Chem. Phys. 16:9974-9986.
3. The D, Grieshammer S, Schroeder M, Martin M, Al Daroukh M, Tietz F, Schefold J, Brisse A (2015) Microstructural comparison of solid oxide electrolyser cells operated for 6100 h and 9000 h. Journal of Power Sources 27: 901-911.
4. Grieshammer S, Nakayama M, Martin M (2016) Association of defects in doped non-stoichiometric ceria from first principles. Phys. Chem. Chem. Phys. 18:3804-3811.
5. Koettgen J, Zacherle T, Grieshammer S, Martin M (2017) Ab initio calculation of the attempt frequency of oxygen diffusion in pure and samarium doped ceria, Phys. Chem. Chem. Phys. DOI: 10.1039/c6cp04802a