Trutz Theuer

 

Electrochemical characterization of differently doped lanthanum based perovskite electrodes and their durability towards chromium poisoning

Schematic setup – Electrochemical impedance spectroscopy with a 3-electrode system Copyright: Sarda, Venkatesh, “An Experimental Investigation into Degradation in a SOFC Anode“, Dissertation RWTH Aachen & Forschungszentrum Jülich GmbH, 2016

A reason for cell degradation of solid oxide fuel cells, is chromium poisoning. Depositions and phase formation of Cr2O3 and SrCrO4 between cathode and the current collector, but also at the cathode/electrolyte interface, decrease the cell performance. With variation of the operation parameters it should be investigated whether a chemical or an electrochemical reaction mechanism is predominant.

The theme of this master thesis will be the electrochemical characterization of symmetrical solid oxide fuel cells (SOFCs) with different cathode materials (e.g LSC, LSCF, LSF) in presence and absence of a chromium source. Besides installation of suitable measuring setups (single cells), it should be focused on the analysis of the impedance and current/voltage characteristics of those cells. To get meaningful results different cathode materials will be characterized regarding temperature, moisture and oxygen partial pressure within previously defined time periods. For the purpose of analyzing the durability of these cathode materials, favored conditions for chromium poisoning should be determined and evaluated via suitable CNLS-fits and equivalent circuit models. Furthermore, additional analysis with help of the “Distribution of Relaxation Times (DRT)” method will be added. Finally first statements about the mechanism of chromium poisoning of lanthanum based perovskite air electrodes (cathodes) should be possible.