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

Abstract

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 metalsupported 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, Co 3 O 4 deposited by atomic layer deposition (ALD), Co 3 O 4 deposited by electroplating deposition (ED), and CuMn 1.8 O 4 (CMO) deposited by electrophoretic deposition (EPD), are explored to enhance the performance of MS-SOECs with La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 −Sm 0.2 Ce 0.8 O 3 (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% H 2 −50% H 2 O. 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.

Ultralow Loading of Ru as a Bifunctional Catalyst for the Oxygen Electrode of Solid Oxide Cells

“…The reversible potential of the samples ranged 0.95−0.97 V, consistent with other SOEC studies using a 50% relative humidity H 2 flow. 31,32 LSCF-5Ru exhibited the best performance with a current density of 656 mA cm −2 at 1.3 V, significantly outperforming LSCF-Bare (440 mA cm −2 at 1.3 V). It is noted that a Ru overcoat with more than 5 ALD cycles resulted in decreased performance.…”

Metal-Supported Solid Oxide Cells for Energy Conversion, Electrolysis, and Chemical Synthesis

“…Multiple cycles of infiltration were used to reach the desired catalyst loading. More details of cell preparation can be found in our previous work (13)(14)(15)(16)(17).…”

“…To address Cr migration, the oxygenside metal support can be coated, Fig 4 . Electrophoretic deposition is a particularly effective deposition technique that coats the interior of the porous support. Such coatings significantly reduce Cr migration during cell fabrication and operation, leading to improved initial performance and durability (13).…”

“…Extremely high surface area promotes high electrochemical reaction rates, but also provides high surface energy leading to coarsening and facilitates Cr deposition. Our recent approaches to mitigating catalyst coarsening and Cr deposition within the cathode include coatings to prevent Cr evaporation from the stainless steel components, and optimization of infiltrated catalyst processing to stabilize the microstructure during operation (13,14).…”

High-Performance Reversible Solid Oxide Cells for Powering Electric Vehicles, Long-Term Energy Storage, and CO2 Conversion

“…Through the application of electrophoretic deposition of a CuMn 1.8 O 4 coating, they demonstrated improved initial performance and long-term stability of MS-SOEC. 22 Despite extensive achievements having been made in either fuel cell mode or electrolysis mode, there are limited studies of employing MS-SOCs to achieve reversible operation. As shown in Figure 1, RSOCs can function either as SOFCs, converting chemical fuels into electrical energy, or as SOECs, utilizing electricity to generate valuable chemicals.…”