2h2 o 4e o2 4e 2o2 load ions through electrolyte

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Unformatted text preview: O2 Load ions through electrolyte Cathode oxygen, usually from air carbon monoxide fuel Anode O 2 2CO + 2O2 ! 2CO2 + 4e O2 + 4e ! 2O2 Load ions through electrolyte Cathode oxygen, usually from air 3 Tuesday, November 5, 13 SOFC Designs Conductivity of electrolyte, electrodes, and interconnects dominates SOFC losses. Thin layers of electrolyte and electrodes are preferred. If they are too thin, mechanical strength will be lost. electrolyte supported cathode supported anode supported anode electrolyte cathode (~100m) (~150m) (~100m) high ohmic loss anode electrolyte cathode (~100m) (~20m) (~1-2mm) cathode oxygen transport limitation anode electrolyte cathode (~1-2mm) (~10m) (~100m) generally favored 4 Tuesday, November 5, 13 c05 JWPR067-Mench January 23, 2008 18:58 Char Count= 5.1 Ion Transport in an Electrolyte 2 Ceramic Electrolytes Yttria-stabilized zirconia (YSZ) -- most commonly used electrolyte Yttria -- Y2O3 Zirconia -- ZrO2 High electrolyte temperature required for oxygen ion transport H2+O2H2O+2eO 2- Oxygen Vacancies Zr 4+ O 2O 2O 2- 2Y 3+ O Zr 4+ O 2- Y 3+ 4+ Y 3+ Zr 4+ Zr 4+ Zr 4+ Zr 4+ 24+ O Y 3+ O 2- Zr O 2- Y 3+ O 2- Zr O 2O O 2- Zr 4+ Y O O 2- 3+ Y 3+ Zr 4+ O 2O 22- Zr 4+ Zr 4+ O 2- O2+4e- 202O2 Y 3+ 2- Zr 4+ Zr 4+ Zr 4+ 2- 4+ O 2- Zr O 2- Anode O 2- Zr 4+ O 2- Zr 4+ O Y 3+ 3+ Y O 2- Y 3+ Zr 4+ Y 3+ 2O Zr 4+ Zr 4+ Zr 4+ O 2- Cathode Electrolyte Typical YSZ -- (ZrO2) 0.92 (Y2O3) 0.08 Figure 5.8 Illustration of oxygen ion transport in ceramic SOFC electrolytes. 80...
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This document was uploaded on 11/20/2013.

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