鑭酸鍶錳(LSM)由於在氧化氣氛下穩定且具備充足導電率(~200S/cm at 800℃)常用來做為固態氧化物燃料電池(SOFC)之陰極，然而由於缺乏離子導電率，包含電子導體、離子導體及氣體的三相界(TPB)被限制在電極及電解質間的界面，由許多研究者藉由將離子導體混入陰極中提高陰極氧還原反應(ORR)之反應面積以降低SOFC陰極之極化阻抗。釔安定氧化鉍(YSB)具有高離子導性與對氧的催化能力，本研究將YSB與奈米級之LSM混合製成複合陰極，由於三相界的延長，陰極之ORR的反應面積增加提高了反應速率並降低陰極之極化阻抗。
然而，包含氧化鉍之複合陰極的氧化原反應速率限制步驟尚未明確，本研究藉由電化學阻抗分析不同YSB含量之LSM-YSB複合陰極在不同溫度下之極化阻抗，不同的YSB含量會影響陰極對氧還原反應的催化能力，然而若使用過量的YSB，LSM將無法形成連續導體並限制住陰極之ORR。
為了研究電解質對陰極的影響，釔安定氧化鋯(YSZ)、釤摻雜氧化鈰(SDC)及YSB被用來做為LSM-YSB複合陰極之電解質，氧離子導性低的電解質會由於氧較難進入氧晶格而使極化阻抗上升。
本研究中當LSM-YSB複合陰極中YSB含量為70vol%且以YSB做為電解質時，在650℃時之及化阻抗僅有0.09ohmcm2，能有如此低的及化阻抗是因為陰極在有連續性導體的前提下有最佳的對ORR催化能力，藉由這些實驗測試將能更明確的瞭解陰極之反應機制。

Lanthanum-strontium manganite (LSM) was the classic cathode material for SOFCs due to its high stability in oxidizing atmospheres, and sufficient electrical conductivity at high temperature (~200S/cm at 800℃). However, insufficient ion conductivity of LSM restricted its oxygen reduction reaction (ORR) to the cathode/electrolyte interface where consist of electronic conductor, ionic conductor, and gas phase (Triple phase boundary, TPB). Several researchers have reported a method to significantly lower cathode polarization resistance (RP) by introducing ionic conductor into SOFCs cathode. Yttria-stabilized bismuth oxides (YSB) which exhibit high ionic conductivity and excellent oxygen electrocatalysis were mixed with nano-sized LSM to form composite cathodes. The extension of ORR site tends to enhance the reaction rate and decrease polarization resistance of the cathode.
In addition, the rate-determining steps for the ORR in bismuth oxide base composite cathode also needs to be explored. In this study, the electrochemical performances of composite cathodes with different LSM:YSB ratio were investigated using electrochemical impedance spectroscopy at various temperatures ranging from 500℃ to 650℃. The YSB content in composite may affect the catalytic activity toward the ORR. However, excessive YSB fraction may cause discontinuity in electronic pathway and then limit ORR of cathode.
To investigate the influence of electrolyte to cathode performance. Yttria-stabilized zirconia (YSZ), samarium-doped ceria (SDC), and YSB electrolyte were used to compare the composite cathode performance with different ionic conductivity electrolyte (ionic conductivity YSB>SDC>YSZ). The electrolyte with low ionic conductivity will increase the impedance of oxygen ion incorporation into oxygen sublattice. The interface of cathode /low ionic conductivity electrolyte limit the cathode performance by increasing polarization resistance.
The RP of LSM-YSB composite cathode shows lowest RP of 0.09 ohmcm2 at 650℃ when the volume fraction of YSB is 70%. The low RP measured from composite cathode is due to the high catalytic ability and sufficient electronic conduction. With the measurement and analysis of polarization impedance, better understanding of the cathodic reaction is achieved.

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