Assessment of Protective Coatings for Metal-Supported Solid Oxide Electrolysis Cells

Green hydrogen is essential to achieving carbon neutrality, and solid oxide electrolysis cells can produce hydrogen using renewable power and waste heat. Insufficient long-term durability of solid oxide electrolysis cells has impeded their commercialization. Here, coatings in the porous stainless steel support of metal-supported solid oxide electrolysis cells (MS-SOECs) are used to dramatically improve their performance and durability. The long-term degradation rate of uncoated MS-SOECs is highly dependent on the current density, with the fastest degradation occurring at the highest current density tested, 0.5 A cm^–2. At this current density, coatings are quite effective. Three protective coatings, Co₃O₄ deposited by atomic layer deposition (ALD), Co₃O₄ deposited by electroplating deposition (ED), and CuMn_1.8O₄ (CMO) deposited by electrophoretic deposition (EPD), are explored to enhance the performance of MS-SOECs with La_0.6Sr_0.4Co_0.2Fe_0.8O₃–Sm_0.2Ce_0.8O₃ (LSCF-SDC) as the oxygen catalyst and SDC-Ni as the fuel catalyst. The initial average current density at 1.4 V is increased with coatings. It is 0.83 mA cm^–2 for the ALD cells, 1.05 mA cm^–2 for the ED cells, and 1.13 mA cm^–2 for the EPD cells, compared to 0.65 mA cm^–2 for the bare cells at 700 °C with 50% H₂–50% H₂O. The degradation rate over 1000 h of continuous operation is reduced from 36% to 26%, 27%, and 19% kh^–1 with the three coatings, respectively. These improvements are ascribed to reduced Cr poisoning on the oxygen catalyst, which is one of the primary degradation modes for this type of MS-SOEC.