Plasma-Enhanced Atomic Layer Deposited Defects Rich ZrO_2-x Nano-Thin Film Stabilized Air Electrode of The Solid Oxide Cells

抄録

As the pressing need for sustainable energy solutions is increasing, solid oxide cells (SOCs), including solid oxide fuel cells (SOFCs) and solid oxide electrolytic cells (SOECs), are actively attracted to move toward clean and renewable energy as the future green energy devices. The key of the SOC is an air electrode, a fundamental component that facilitates the oxygen reduction reaction (ORR). Perovskite oxides, in particular, Sr-based perovskite oxides such as SFM (Sr₂Fe_1.5Mo_0.5O_6-δ), BSCF (Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ), and LSCF (La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ) stand out as high-performance air electrode materials, boosting remarkable electrochemical properties that position them as ideal candidates for enhancing the ORR performance of SOCs.A notable challenge inherent to Sr-based perovskite oxides employed as SOC electrodes is the poor stability. The Sr segregated on the surface under the high operation temperature and the segregated SrO further reacted with H₂O and CO₂ in the air forming insulating impurity phases (Sr(OH)₂, SrCO₃) on the surface, which passivate the ORR activity.The coating on the perovskite is an efficient way to prohibit the degradation behavior of the perovskite oxide air electrode. Thermochemically stable materials coating layers act as physical protection layers to prevent the segregated SrO on Sr-based perovskite oxides from reacting with CO₂ and H₂O in the air and forming impurities. However, the coating layer will be occupied at the reaction site will lead to poor ORR activities. Hence, the fabrication of finely covered, ORR active, and thermochemically stable thin film on the Sr-based perovskite oxides surface is the key to this coating strategy.In this study, we applied defects-rich ZrO_2-x film on the SFM perovskite surface by plasma-enhanced atomic layer deposition (PE-ALD). The 15 nm ZrO_2-x film covered the porous SFM air electrode uniformly. The defects in the ZrO_2-xfilm were directly observed by TEM, enabling the ZrO_2-x an oxygen ionic conductor, rather than completely insulating. The distribution of relaxation times analysis (DRT) reveals the oxygen ions immigration process was enhanced after coating the ZrO_2-x thin film on the SFM. The polarization resistance of the 15 nm ZrO_2-x coated SFM air electrode shows the same as the bare SFM electrode at 0 hour but only 34 % of the bare SFM after operation under 800 ℃ for 50 hours. The results showed that coating ZrO_2-x film on the SFM surface effectively promoted the stability of the SFM perovskite oxide air electrode. This innovative approach holds immense potential for elevating the performance and long-term durability of high-temperature energy devices, especially air electrodes within solid oxide cells (SOC) or metal-air batteries.