Dense Mn1.5Co1.5O4 coatings with excellent long-term stability and electrical performance under the SOFC cathode environment

Abstract

The long-term operation of intermediate temperature-solid oxide fuel cells (IT-SOFCs) could be significantly influenced by the stability of the interconnect itself, especially, its oxidation resistance under the cathode environment. In this work, dense 80-μm-thick Mn1.5Co1.5O4 (MCO) coatings were directly applied on T441 interconnects via cost-effective atmospheric plasma spray (APS) without any post-treatment. The MCO-coated T441 interconnect and La0.8Sr0.2MnO3(LSM)//MCO/T441 contact coupling were separately exposed to high-temperature oxidative environment to evaluate their long-term oxidation resistance and electric performance. A rather low area-specific electrical resistance (ASR) of 13 mΩ·cm2 was obtained for MCO-coated T441 at the end of 2000-h test cycle, and a similar decrement was observed for the LSM-MCO/T441 couple with a final ASR of 13.6 mΩ·cm2 at the end of 1200-h cycle. Electron back scattering diffraction was performed to explore the oxidation characteristic of the MCO/T441 interface. In addition, first-principles computations were conducted to evaluate the structural stability of various possible interfacial oxides using the Castep program based on the density functional theory. The results indicated that the APS-MCO coating exhibits high grain stability and effectively improves the oxidation resistance of the T441 interconnect during long-term operation under the SOFC cathode environment.