Method to Measure Area Specific Resistance and Chromium Migration Simultaneously from Solid Oxide Fuel Cell Interconnect Materials

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.

Reactivation of chromia poisoned oxygen exchange kinetics in mixed conducting solid oxide fuel cell electrodes by serial infiltration of lithia

“…30 Chromium is well known to be the most pervasive extrinsic surface poison for SOFCs and is inherent to the operation of fuel cell stacks. [31][32][33][34][35] Ferritic steels with a chromium content between 18 and 25% are well suited interconnect materials, given their need to be simultaneously electronically conducting, oxidation resistant, impermeable to gas diffusion, stable and compatible with the other fuel cell materials, as well as being inexpensive. 36 Unfortunately, Cr inevitably finds its way from the interconnect to the cathode during operation via vapor phase or surface diffusion.…”

Addressing planar solid oxide cell degradation mechanisms: A critical review of selected components

“…The difficulty in the modeling approaches arises from the wide range of testing conditions and the influence of the gas atmosphere. Usually, ex situ characterization methods of protective coatings involve chromium evaporation measurements, ASR measurements, and long‐term exposure tests 270,271 …”

Accelerated Stress Tests for Solid Oxide Cells via Artificial Aging of the Fuel Electrode

“…For the improvement and optimization of SOCs' long-term performance, it is important to identify and quantify the degradation sources and to use them as a base for the development of successful mitigation strategies [7,8]. On the cell and stack levels, there are numerous studies on the degradation of cell components with emphasis on electrodes, electrolytes, and interconnects [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. However, the picture is more complicated, since the degradation processes are related to the cell/stack design, operating conditions, geometrical and technological factors, quality of the raw materials, precision of the instrumentation, preconditioning, testing protocols, and predictable and unpredictable failures [25][26][27][28][29].…”