In-situ experimental benchmarking of solid oxide fuel cell metal interconnect solutions

The progress in the diffusion of solid oxide fuel cell (SOFC) as commercial devices is not paired by literature production. Articles describing the behaviour of SOFC stacks are rare because of confidentiality reasons for commercial suppliers while research centres prefer to focus on single components or low technology readiness level research. This article aim to fill this gap presenting the analysis of three short stacks run in operative conditions for 10 000 h each. The stacks are characterized through voltage vs time curves, electron microscopy, and electro-chemical impedance spectroscopy. Focus is given on the interconnect; notably on the different types of coatings, varying for composition (MnCo2O4, MnCo1.8Fe0.2O4) and deposition technique (atmospheric plasma spray-APS, physical vapour deposition-PVD, wet powder spraying-WPS). Nitriding of the steel substrate as a solution to improve the chromium retention properties is tested as well. Results: indicate that coating deposition technique is the most important parameter, with single repeat unit (SRU) containing PVD coating showing the lowest voltage degradation rate. Commercial ferritic stainless steel K41 confirmed to be a reliable choice if coupled with a coating. Moreover, SRU containing WPS coating demonstrated to be more reliable than expected from standard area specific resistance 4-probe test.