No abstract

Chromium evaporation is identified as a major degradation mechanism in solid oxide fuel cell (SOFC) stacks. The major chromium source is the commonly used stainless steel interconnects, thus raising a need for protective coatings on the interconnect steel. Ex situ characterization methods of protective coatings involve chromium evaporation measurements, area specific resistance (ASR) measurements and long‐term exposure tests. To replicate stack conditions, commonly used ASR measurement setups should be further developed. This work presents an improved characterization method for steels and coatings and aims to be an extension to state‐of‐the‐art characterization methods. The studied steel samples, bare or coated, are placed adjacent to palladium foils with a screen‐printed lanthanum‐strontium‐cobalt (LSC) layer and the resistivity over the pair is measured. The method offers similar contact materials, chromium migration mechanisms, electrical contacts and chemical interactions, as seen in stacks. Further, it enables post‐test chromium migration analysis with electron microscopy. Demonstration of the method validated that protective coatings hindered both oxidation and chromium migration from the substrate steels. The presented method could aid in accelerating protective coating development.

Efficient operation of solid oxide fuel cell (SOFC) stacks requires uniform temperature and fuel utilization distributions in the stack. Especially high fuel utilizations necessitate uniform fuel flow distributions to avoid performance decrease or anode reoxidation. A uniform temperature distribution helps to prolong the life-time of the stack. This work presents a method to determine the fuel utilization and temperature distribution in SOFC stacks with electrochemical impedance spectroscopy (EIS). The equations for relating the measured impedance and fuel utilization and temperature are derived from physical equations describing the SOFC stack. The method is demonstrated with an ElringKlinger AG 10-cell stack fuelled with 50%/50% H 2 /N 2 at nominal operation conditions. The difference in temperature and fuel utilization between cells was determined. The calculated distributions are in line with cell voltage measurements. The method can be used to improve SOFC stack design and performance.

Stainless steel interconnect materials used in solid oxide fuel cells and electrolysers need to be coated to improve oxidation resistance and to mitigate Cr-vaporization. This work aimed to explore the optimal steel/coating combinations suitable for use in reversible solid oxide stacks and evaluated (Co,Mn)3O4 spinel, LaFeO3 perovskite, Ce/Co and Y-based coatings, on AISI441 and Crofer 22 APU steels. The coatings were evaluated based on measurements of mass gain and oxide scale thickness after exposure at 700 and 800 °C to fuel side (90 vol.% H2O/10 vol.% H2) and air/oxygen side (pure O2) atmospheres. In pure O2, the most efficient coatings for limiting oxide scale formation and Cr evaporation, compared to the bare steel, were (Co,Mn)3O4 and CeCo on Crofer 22 APU. In 90 vol.% H2O/10 vol.% H2, the Y-based coating showed the largest improvement in oxidation resistance.

Ever-tightening regulations has caused shipping industry need to look for alternatives for conventional fuels. Hydrogen is seen as one of the key contributors in mitigation of emissions from shipping. The FLAGSHIPS project is an EU funded co-operative which aims to raise the readiness-level of hydrogen and fuel cell technologies in shipping by deploying two hydrogen fuel cell powered vessels. One of the vessels is a self-propelled barge in Paris, France and the other one is passenger and car ferry in Stavanger, Norway. This paper presents the status of the project and discuss the key learnings in the project so far.