Electrochemical oxygen reduction on solid electrolytes: Structure-property relations of perovskite-type model electrodes

02.01.2010 - 31.10.2014
Research funding project
In this project the electrochemical oxygen exchange taking place at perovskite-type electrodes on solid electrolytes is in the focus of research. This reaction is highly relevant from a fundamental point of view (model reaction in solid state electrochemistry) but also due to its importance in solid oxide fuel cells (SOFCs), gas sensors and other electroceramic devices. Active reaction sites of the electrochemical oxidation/reduction are either on the electrode surface or at the three phase boundary where oxygen, electrolyte and electrode meet. The effect of surface chemistry (e.g. surface cation composition, segregation), surface and bulk crystal structure and microstructure on the reaction kinetics is largely unknown and degradation or activation phenomena of electrodes are also not well understood. It is the goal of this project to investigate and quantify structure-property relations of perovskite-type electrodes and to better understand the elementary mechanisms and the functional role of the surface qualities governing the kinetics of the electrochemical oxygen exchange. The following key questions will be considered: i) What is the role played by surface composition, crystal structure and microstructure of perovskite-type electrodes in the kinetics of electrochemical oxygen reduction? ii) What are the reasons for degradation and activation of perovskite-type electrodes? iii) What are the reaction rates at three phase boundaries? iv) What is the exact reaction mechanism of oxygen reduction / oxide ion oxidation? In order to contribute to the solution of these questions, defined thin film microelectrodes ((La,Sr)CoO3-, (La,Sr)MnO3 on yttria stabilized zirconia) will be prepared by pulsed laser deposition and lithography and their electrochemical properties will be investigated by impedance spectroscopy and I-V measurements. The surfaces will be systematically varied by different preparation conditions, thermal and voltage treatment and by ion beam etching for ¿in-situ¿ creation of new surfaces and three phase boundaries. Chemical and structural information will become available from HRTEM, EELS, TOF-SIMS, XRD and AFM studies performed by collaboration partners. Reaction kinetics at three phase boundaries will be investigated via additional micro-structuring of microelectrodes, extrapolation of data under anodic polarization and by specially designed multilayer microelectrodes which allow electrochemical oxygen reduction only close to three phase boundaries. Additional mechanistic information will be obtained from p(O2) and voltage dependent experiments. These studies should allow us to significantly improve the understanding of electrochemical oxygen reduction on perovskite-type electrodes.

People

Project leader

Project personnel

Institute

Grant funds

  • FWF - Österr. Wissenschaftsfonds (National) Austrian Science Fund (FWF)

Research focus

  • Non-metallic Materials: 40%
  • Climate Neutral, Renewable and Conventional Energy Supply Systems: 30%
  • Surfaces and Interfaces: 30%

Keywords

GermanEnglish
Brennstoffzellenfuel cells
Elektrodenelectrodes

Publications