Mn-Co spinel coating for Fe-22Cr interconnects toward scalable seawater SOEC

To mitigate interconnect corrosion in seawater-fed solid oxide electrolysis cells (SOECs), Mn 1.5 Co 1.5 O 4 spinel coatings were deposited on Fe-22Cr stainless steel. At 750 °C, the coated interconnects exhibited an area-specific resistance (ASR) of 31.8 mΩ cm 2 after 4835 h of oxidation in air, with a parabolic rate constant of 3.0 × 10 −5 mg 2 cm −4 h −1 . Following exposure to seawater vapor for 500 h, the ASR reached 3.36 mΩ cm 2 , with a predicted value of 9.80 mΩ cm 2 at 5000 h. These findings underscore the coating’s improved oxidation resistance under dual-atmosphere conditions. Furthermore, a three-cells stack demonstrated high stability with a low degradation rate of 1.04 × 10 −5 h −1 at 100 mA cm −2 for 100 h. Post-test analysis confirmed a crack-free structure with negligible additional resistance, indicating that the spinel coating satisfies the engineering requirements for durable, direct seawater electrolysis and provides a scalable pathway for green hydrogen production.