陽極負載複合氧化鈰電解質中溫固體氧化物 燃料電池之製備與性能研究

Fabrication and Investigation of Anode-supported Intermediate Temperature Solid Oxide Fuel Cells with Composite Ceria-based Electrolyte Films

鍾振泓(Cheng-Hung Chung)

指導教授 ： 鄭淑芬

國立臺灣大學/理學院/化學研究所/博士(2008年)

https://doi.org/10.6342/NTU.2008.01042

摘要

以檸檬酸溶膠凝膠燃燒法合成Ce0.8Gd0.2O2-δ (CGO)粉末，摻雜少量金屬氧化物製備複合電解質（1mol% Bi2O3, GeO2, Nb2O5），結果顯示可以改進CGO基材緻密化，也改進其導電率，並且長時間（∼85h）在10% H2/N2還原氣氛下，也能維持材料的化學穩定性。由於台灣濕氣環境，以麵粉輔助式乾壓法製備陽極負載型中溫固態氧化物燃料電池（IT-SOFC），電解質材料使用低溫燃燒法( ~ 280℃)之CGO粉末，所製作的單電池陽極（60wt%-NiO/CGO），陰極（La0.8Sr0.2Co0.8Fe0.2O3-δ）與CGO電解質厚度分別為16 ± 2、493 ±7、153 ± 4 μm。採用自行架設裝置，測量單電池效能，以50ml/min 100% H2及150ml/min Air最佳化流速下，700℃最大功率密度（PPD）及開路電壓（OCV）約為450 mW/cm2及0.79V；以50ml/min 100% H2及90ml/min 100%O2最佳化流速下約為504 mW/cm2及0.82V，其速率決定步驟（RDS）在550℃以下時為氧分子還原反應控制，600℃以上時為歐姆極化控制。當電池改變電解質材料下，以1mol% GeO2複合CGO後，在最佳化流速下陰極端為空氣、100% O2時，700℃下其PPD約為462、521 mW/cm2，分別改進了約12、17 mW/cm2；當電池改變陰極材料下，以5.02wt% Pt複合LSCF後，相同的最佳化流速下陰極端為空氣、100% O2時，700℃下其PPD 約為526、582 mW/cm2分別改進約76、78mW/cm2。當電池改變陽極材料下，2.5wt%Mn-Ni/CGO複合陽極於700℃的氫氣、甲烷（5ml/min）下之電池功率，分別只有純Ni/CGO陽極的2/5、3/5倍，並且電池效能隨時間而持續老化。
建議原因如下：以1mol% GeO2複合CGO後，氧離子導電率（σi）增加，因此電池效能獲得改善，然而以 (≦1mol% Bi2O3, Nb2O5) 複合CGO後，反而導致電池嚴重內短路。複合Pt/LSCF陰極，由於Pt材料氧離子導電率低，且不同複合量Pt會引起陰極微結構的變化，因此複合量有極值。複合Mn-Ni/CGO陽極，由於陽極形貌產生緻密化現象而導致表面積減少，即陽極活性惡化，因此並沒有改進直接甲烷下的電池效能。

關鍵字

IT-SOFC ； CGO ； 60wt%-NiO/CGO ； LSCF

並列摘要

Ce0.8Gd0.2O2-δ (CGO) powder samples were synthesized using citrate sol-gel combustion method, and then the composite electrolyte materials were prepared by a small amount of 1mol% Bi2O3, GeO2, Nb2O5 to CGO.
The results show that the densification and conductivity of composite electrolyte were improved. In addition, undergoing 10% H2/N2 for ~ 85h, the conductivity at 700°C in air of the samples could be retained nearly at their starting conductivity.
The fabrication of anode-supported intermediate temperature solid oxide fuel cell (IT-SOFC) was carry out by using sandwiched dry-pressed technique with flour layers, because of humid environment in Taiwan, ultrafine CGO powder as electrolyte material. The single cell showed that electrolyte was 16 ± 2 μm in most thin thickness, anode (60wt%-NiO/CGO) and cathode (La0.8Sr0.2Co0.8Fe0.2O3-δ) were 493 ± 7 and 152 ± 4 μm in thickness, respectively. At our best knowledge to build the electrochemical testing device, and the performances of single cell were ~ 450 mW/cm2 (PPD) and ~ 0.79V (OCV), while 100%H2 and air with optimum flow rate of 50 and 150 mL/min at 700°C. On the other hand, under 100%H2 and 100%O2 with optimum flow rate of 50 and 90 mL/min, the the performances were ~ 504 mW/cm2 and ~ 0.82V.
The rate-determining step (RDS) was depended on operation temperature: Under 550°C, RDS was oxygen reduction reaction. Above 600°C, RDS was ohmic loss. To exchange of electrolyte material, the addition of 1mol% GeO2 to CGO film was made, under the optimum flow rate through air and 100%O2 in turn, the PPD of single cell were ~ 462 and ~ 521 mW/cm2, respectively, which were improving ~ 12 and ~ 17 mW/cm2, respectively.
To exchange of cathode material, the addition of 5.02wt% Pt to LSCF cathode was made, under the optimum flow rate through air and 100%O2 in turn, the PPD of single cell were ~ 526 and ~ 582 mW/cm2, respectively, which were improving ~ 76 and ~ 78 mA/cm2, respectively.
To exchange of anode material, the addition of 2.5wt% Mn to Ni/CGO anode was made, under flow rate of 5mL/min through 100%H2 and 100%CH4 at 700°C in turn, the sample displayed about one-third and three-fifth times of the performances of pure Ni/CGO anode, in addition, the performance decreased with long-time.
The primary reasons were suggested following: the addition of 1mol% GeO2 to CGO was improving oxide-ion conductivity of electrolyte, thus the influence improved the performance of single cell. However, a small amount of 1mol% Bi2O3 or Nb2O5 to CGO was deteriorating short-circuit short-circuit of electrolyte. For composite Pt/LSCF cathode, the adequate amount of Pt to LSCF was selected due to low oxide-ion conductivity and optimum microstructure surface of self. For composite Mn-Ni/CGO anode, the dense microstructure on surface was observed by the addition of Mn to Ni/CGO , thus the performance of single cell was deteriorating for the direct electrochemical oxidation of methane.

並列關鍵字

IT-SOFC ； CGO ； 60wt%-NiO/CGO ； LSCF

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