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. Furthermore, 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.