| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 96 === In this work, we study the cathode performance of (La1-ySry)(CoxFe1-x)O3 (y=0.1~0.4，x=0.1~0.9) LSCF coupled with the electrolyte (La1.8Dy0.2)(Mo1.6W0.4)O9 LDMW. A (Sm0.2Ce0.8)O1.9 SDC layer is applied between cathode and electrolyte to impede the interdiffusion between Sr and Mo, which produces SrMoO4 and drastically increase the oxygen reduction reaction (ORR) resistance. The structure and morphology are investigated using X-ray diffraction XRD and scanning electron microscopy SEM. The electrochemical performance is focused on the ORR loss measured on the symmetric electrode of half cell using impedance spectroscopy and Tafel plot recorded by a potentiostat.
The XRD results indicate that the LSCF cathode possesses perovskite structure of rhombohedral cell, no secondary phase detected. With increasing Co content, several diffraction peaks begin to split. The phase of SrMoO4 has been detected in the mixture of LSCF and LDMW after heating at 800�a℃ for 6 h. A dense product layer has also been observed between the LSCF cathode and LDMW electrolyte in the SEM micrograph.
The half cell of symmetric electrode has been prepared by coating the LDMW electrolyte on both sides with SDC paste and sintered at 1000�a℃ for 2h, then coating LSCF on both sides and sintered at 800�a℃ for 2h. The impedance spectroscopy analysis indicates that (La0.6Sr0.4)(Co0.8Fe0.2)O3 exhibits the minimum ORR resistance, 0.858 Ω•cm2 at 700�a℃.
The measured ORR resistance by impedance spectroscopy is consistent with the ion exchange current density measured by CorrView software. The ion exchange current density is 18.3 mA/cm2 at 700�a℃.
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