Co₃O₄/Sm-Doped CeO₂/Co₃O₄ Trilayer Coating on AISI 441 Interconnect for Solid Oxide Fuel Cells

In this work, a novel Co/Sm-doped CeO₂ (SDC)/Co trilayer of ∼6 μm is deposited by alternating electrodeposition and electrophoresis and oxidized to a Co₃O₄/SDC/Co₃O₄ trilayer structure. This coating is unique and effective in the following aspects: (1) The area specific resistance of the coated interconnect is more stable and lower than that of the uncoated interconnect after thermal treatment at 800 °C for 400 h. (2) The Co₃O₄/SDC/Co₃O₄ coating layer can effectively inhibit Cr diffusion and evaporation and significantly slow the oxidation rate of the interconnect. (3) The Sm_0.5Sr_0.5Co_0.2Fe_0.8O₃ cathode in the electrolyte/cathode/interconnect half-cell retains its initial stoichiometry after 100 h of the thermal treatment. Subsequently, the ohmic resistance R_Ω, high frequency polarization resistance R_H, and low frequency polarization resistance R_L of the half-cell with the Co₃O₄/SDC/Co₃O₄ coated interconnect are all smaller than those of the half-cell with the bare interconnect. The Co₃O₄/SDC/Co₃O₄ coating layer has great advantages to be used as a protective layer for the metallic interconnect in solid oxide fuel cells to improve cell performance, stability, and durability.