Chemical state identification of Ce^3 +/Ce^4 + in the Sm_0.2Ce_0.8O_{2 鈭?#xa0;未} electrolyte for an anode-supported solid oxide fuel cell after long-term operation

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• 作者：Tai-Nan Lin ; Maw-Chwain Lee ; ^{mclee@iner.gov.tw} ; Rung-Je Yang ; Jen-Chen Chang ; Wei-Xin Kao ; Ling-Song Lee
• 关键词：Cerium valence state ; Thin film ; Degradation ; XPS ; Phase transformation
• 刊名：Materials Letters
• 出版年：2012
• 期刊代码：59_0167577x
• 类别：ms
• 出版时间：15 August, 2012
• 卷：81
• 期：Complete
• 页码：185-188
• 文件大小：1361 K

摘要

Direct evidences of cerium valence state transformation from Ce^4 + to Ce^3 + in an anode-supported solid oxide fuel cell after long-term operation have been identified. Single cell with samarium-doped ceria (Sm_0.2Ce_0.8O_{2 鈭?#xA0;未}, SDC) thin film electrolyte is prepared with maximum power density of 608 mW cm^鈭?#xA0;2 at 650 掳C when the fuel/oxidant flow rates are 335/1005 sccm, respectively. The long-term durability tests are executed by fixed-current operation for 950 h. The power density and voltage degradation are observed and critically attributed to the chemical state transformation of cerium in the electrolyte. From X-ray photoelectron spectroscopy (XPS), the Ce^3 + ratio increases from 30.3 to 52.9%in the electrolyte before and after operation. The focused ion beam (FIB)/transmission electron microscopy (TEM) techniques are utilized to investigate the structure variation and the selected area diffraction patterns of the chosen grains towards electrodes identify the phase transformation from CeO₂ to Ce₂O₃, suggesting that the Ce^3 + species increase at the near-anode side. The direct evidence of Ce^3 + presence shows one of the key factors for the degradation of a low temperature solid oxide fuel cell (LT-SOFC).