不同水氣分壓對固態電解質BaCe0.8-xZrxY0.2O3-δ電化學性質之影響

The Effect of Different Water Vapor Pressure on Electrochemical Properties of BaCe0.8-xZrxY0.2O3-δ Solid Oxide Fuel Cell Electrolyte

李宥辰(Yu-Chen Lee)

指導教授 ： 洪逸明

元智大學/工程學院/化學工程與材料科學學系/博士(2013年)

https://doi.org/10.6838/YZU.2013.00133

摘要

本研究目的在探討陽離子摻雜對BaCe0.8Y0.2O3-δ電解質導電率與相穩定性之影響，在前人研究中發現BaCe0.8Y0.2O3-δ具有最高導電率，但穩定性易受到水分的破壞，故本研究採用摻雜的方式，以增加BaCe0.8Y0.2O3-δ導電性或穩定性。實驗採用固相反應法製備BaCe0.8-xZrxY0.2O3-δ (x＝0～0.2)。
結果顯示：由XRD圖譜得知，利用溶液法所製備BaCe0.8-xZrxY0.2O3-δ各成份皆為單一鈣鈦礦結構；在導電率方面，BaCe0.8-xZrxY0.2O3-δ各成份皆隨著溫度上升而增加，BaCe0.8Y0.2O3-δ導電率最高於800 oC、PH2O＝0.03 atm空氣下為0.025 S/cm；BaCe0.65Zr0.15Y0.2O3−δ電率最高當操作條件於800 oC、PH2O＝0.30 atm空氣下為0.057 S/cm；BaCe0.7Zr0.1Y0.2O3−δ電率最高於800 oC、PH2O＝0.80 atm空氣下為0.095 S/cm。另外由交流阻抗分析得知，BaCe0.8-xZrxY0.2O3-δ各阻抗皆隨溫度上升而下降，各溫度所呈現的阻抗皆以晶界阻抗為主，較晶粒阻抗及離子擴散阻抗大許多，並且BaCe0.8Y0.2O3−δ具有最小的晶粒阻抗度。在相穩定性方面，在BaCe0.8Y0.2O3-δ所呈的穩定性最差，在80 oC水中8小時後，主相的強度明顯下降並產生雜相，而當Zr4+取代Ce4+，由XRD圖譜可以發現穩定性明顯提升，鈣鈦礦主相不易受到水分破壞可以抵抗水破壞達48小時，而到144小時後，所有樣品得主相皆受到水的破壞。單電池測試中，並無破裂情形產生在電解質薄膜中，在開路電壓(OCV)皆有達到0.9 V以上，OCV隨著溫度下降而上升，並且所有電池樣品在700 oC有最大輸出功率。而在800 oC、高水氣分壓操作後，所有樣品性質急遽下降，原因為水氣與陽極材料反應，使得陽極體積膨脹，陽極及電解質介面破裂，造成電池性能下降。

關鍵字

固態氧化物燃料電池 ； 鋇鈰酸固態電解質 ； 質子導性 ； 交流阻抗分析

並列摘要

In this study, the structure, phase stability, and conductivity properties and cell of BaCe0.8-xZrxY0.2O3−δ (x＝0～0.2) at different water vapor pressure were investigated. XRD results indicate that the BaCe0.8-xZrxY0.2O3−δ samples transform from the symmetric cubic structure to asymmetric orthorhombic structure. The conductivity of BaCe0.8-xZrxY0.2O3−δ increases with temperature increased. At 800 oC, the highest conductivity of BaCe0.8Y0.2O3−δ, BaCe0.65Zr0.15Y0.2O3−δ, BaCe0.7Zr0.1Y0.2O3−δ sample is 0.025 S cm−1 at PH2O＝0.03 atm, 0.057 S cm−1 at PH2O＝0.30 atm, and 0.095 S cm−1 at PH2O＝0.80 atm, respectively. All of resistances significantly decreased as the temperature increased. However, it was found that the main resistance comes from grain boundary, which effect is much higher than the bulk resistance and oxygen ion diffusion resistances. BaCe0.8Y0.2O3−δ had the lowest value of bulk boundary resistance. In the result of phase stability, it was found that the intensity of the perovskite phase decreased and secondary phase formed especially for the BaCe0.8Y0.2O3-δ sample in 80 oC water bath after 8 hours. The phase stability of BaCe0.8-xZrxY0.2O3−δ (x＝0.05～0.2) samples is better than that of BaCe0.8Y0.2O3-δ. BaCe0.8-xZrxY0.2O3−δ (x＝0.1～0.2) exhibits no second phase in 80 oC water bath after 48 h. The open-circuit voltages of all cells are above 0.9 V; therefore, it can be sure no continuous channel existed in BaCe0.8-xZrxY0.2O3−δ(x＝0～0.2) electrolyte film. The open-circuit voltages of all cells decreased as the temperature increased. The maximum power density of all cells appeared at 700 oC. Serious distortion of the cell based on BaCe0.7Zr0.1Y0.2O3-δ electrolyte shut down the output performance when operating at 800 oC and high water vapor pressure condition. The cracks and distortion generated in the layer of anode are due to the tremendous volume expanded on the anode electrode in the higher air humidity atmosphere.

並列關鍵字

Solid Oxide Fuel Cell ； BaCeO3-based Electrolyte ； Protonic Conductor ； Electrochemical Impedance Spectra (EIS)

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