Redox stability and electrochemical study of nickel doped chromites as anodes for Hb>2b>/CHb>4b>-fueled solid oxide fuel cells

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• 作者：Vicente B. Vert ; Francisco V. Melo ; Laura Navarrete ; Jos&eacute ; M. Serra ; ^{jmserra@itq.upv.es}
• 关键词：Anode ; Chromites ; Redox cycle ; Nickel ; Nanoparticle ; Redox cycling ; Methane steam reforming
• 刊名：Applied Catalysis B ; Environmental
• 出版年：2012
• 期刊代码：4_09263373
• 类别：ce
• 出版时间：5 April, 2012
• 卷：115-116
• 期：Complete
• 页码：346-356
• 文件大小：1312 K

摘要

The influence of nickel and strontium incorporation in LaCrOb>3b> on the crystalline structure, redox behavior and electrochemical performance by impedance spectroscopy using symmetrical cells has been studied. Namely, the Lab>1鈭?em>xb>Srb>xb>Crb>1鈭?em>yb>Nib>yb>Ob>3鈭?em>未b> (x = 0, 0.15; y = 0.05, 0.1, 0.2) system was investigated. Structural and redox evolution has been monitored by X-ray diffraction in oxidized and reduced samples. Reduced samples kept the initial perovskite structure although metallic nickel nanoparticles were detected on the perovskite grain surface by TEM analysis. The re-oxidized surface did not present nickel particles, suggesting the nickel re-incorporation into perovskite lattice coupled with cation diffusion. The perovskites were tested as SOFC anodes and the polarization resistance depended on the nickel stoichiometry and the reduction temperature. Lab>0.85b>Srb>0.15b>Crb>0.9b>Nib>0.1b>Ob>3鈭?em>未b> reduced at 800 掳C showed the lowest polarization resistance, both in hydrogen and methane. In fact this composition showed a 20%methane conversion at 900 掳C for the methane steam reforming in a fixed bed reactor. Tolerance to redox cycling was proved electrochemically by in situ treatments of Lab>0.85b>Srb>0.15b>Crb>0.9b>Nib>0.1b>Ob>3鈭?em>未b> electrode. Materials were further analyzed by TPR and XPS (in oxidized and reduced state) in order to identify the possible species involved in the electrocatalytic processes.