A pinboard by
Alexandra Ploner

PhD, Technical University of Denmark


Investigation of steam as stressor for accelerated lifetime testing of Ni-YSZ electrodes

To date, huge effort has been dedicated to the development of highly performing and stable Solid Oxide Fuel Cells (SOFC). Consequently, obtaining durability/lifetime data under nominal conditions involves prolonged testing periods and high costs, as the lifetime requirements for different applications vary from 2 to 10 years. This critical issue is mainly responsible for the delay in commercialization of the technology. In order to shorten experimental testing times different accelerated testing methods (ALT) are implemented for so called reliability engineering. For ALT testing stressors need to be identified to activate and fasten the targeted failure mode and minimize unexpected effects. However, in a fuel cell stack, this is challenging as the system comprises various components with different dependencies of degradation mechanisms upon various operation conditions, i.e. steam, current density and temperature. Thus, the work on ALT testing for fuel cells and in particular SOFC is rather limited. This study focusses therefore on possible ways for accelerated lifetime testing of SOFCs, in particular on stressors affecting degradation of Ni-Yttria-stabilized zirconia (Ni/YSZ) cermet electrodes – the most frequently used fuel electrode in SOFC. It appears to be the electrochemically limiting cell component in state-of-the-art cells and so should be of particular concern for the developers of accelerated testing methods. At present, operating parameters such as steam content and temperature are considered to mainly affect the degradation of Ni-YSZ electrodes. This study concentrates on experimentally identifying the acceleration impact of steam and its limits for the fuel electrode via electrochemical impedance spectroscopy analysis. Furthermore, the responses of two different initial microstructures of the Ni-YSZ electrode towards steam as accelerating impactor are evaluated. This data is needed to establish a lifetime prediction model for industrial purposes.