Browsing by Author "Hsieh, Wen-Shuo"

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Characteristics of electrolyte supported micro-tubular solid oxide fuel cells with GDC-ScSZ bilayer electrolyte
(2014-10-13)
Hsieh, Wen-Shuo
;
Lin, Pang
;
Wang, Sea-Fue
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this study, a gadolinia-doped ceria (GDq-supported micro tubular SOFC (T-SOFC) was fabricated using extrusion and dip-coating techniques (Cell A). The effects of inserting a scandium-stabilized zirconia (ScSZ) layer as an electron blocking layer between the GDC layer and the GDC-Ni anode layer were also explored (Cell B). The microstructures and electrochemical performances of Cell A and Cell B were investigated and compared. The layer thicknesses of the GDC and ScSZ bi-layer electrolytes were approximately 285 mu m and 8 mu m respectively. With the inserted ScSZ layer, both the ohmic resistance and the polarization resistance significantly increased at all the operating temperatures. The increase in the ohmic resistance of Cell B was predominantly due to the interfacial resistance, while the substantial escalation in the polarization resistance was mainly because of the low bulk oxygen diffusion process in the ScSZ layer and the smaller charge transfer processes occurring at the interfaces. The OCV of Cell B showed a slight decrease from 1.06 to 0.98 V and that of Cell A experienced an obvious decline from 0.92 to 0.76 V as the temperature rose from 650 to 800 degrees C. The ScSZ layer of Cell B successfully inhibited the OCV loss caused by the electronic conduction in GDC. The maximum power densities (MPDs) of Cell A at 650, 700, 750, and 800 degrees C were 0.20, 0.27, 0.33, and 0.36 Wcm(-2), and those of Cell B 0.16, 0.23, 0.32, and 0.42 Wcm(-2). The MPD of Cell B was improved at temperatures above 750 degrees C but remained inferior to that of Cell A below 750 degrees C. This is due to the fact that, as operating temperature increased above 750 degrees C, the benefit of the higher OCV in Cell B surpassed the deficiency of the higher cell resistance, thereby leading to a higher MPD. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Effects of cathode materials on the characteristics of electrolyte supported micro-tubular solid oxide fuel cells
(2014-05-01)
Hsieh, Wen-Shuo
;
Lin, Pang
;
Wang, Sea-Fue
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The effects of the GDC-LSCF (Ce0.8Gd0.2O0-delta-La0.6Sr0.4Co0.2Fe0.8O3-delta) cathode layer and the GDC interlayer on the electrochemical performance of the ScSZ (Zr0.8Sc0.2O2-delta) electrolyte supported (approximate to 270 mu m) micro-tubular SOFC cells are investigated in this study. Material formulation and sintering profile for fabricating the micro-tubular SOFC cells are developed to avoid physical defects caused by the large sintering shrinkage mismatch among the layers. Cell B (with the LSCF-GDC composite cathode layer and the GDC interlayer) reports an ohmic resistance slightly higher than that of Cell A (with the GDC -La0.8Sr0 2MnO3-delta., i.e. LSM, composite cathode), while its polarization resistance emerges to be significantly smaller than that of Cell A. In terms of cell performance, Cell B demonstrates an OCV value (>1.07 V) similar to that of Cell A and a maximum power density (0.26W cm(-2)) 44.4% greater than that of Cell A (0.17 W cm(-2)) at 850 degrees C. It can thus be concluded that using the LSCF-GDC composite-cathode layer and inserting the GDC interlayer help reduce the total cell impedance, thereby improving the power density of the tubular cells. (C) 2013 Elsevier B.V. All rights reserved.
Fabrication of electrolyte supported micro-tubular SOFCs using extrusion and dip-coating
(2013-02-27)
Hsieh, Wen-Shuo
;
Lin, Pang
;
Wang, Sea-Fue
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Dense electrolyte supported micro tubular solid oxide fuel cells (T-SOFCs) were prepared in this study. Green Zr0.8Sc0.2O2 - delta (ScSZ) electrolyte micro-tubes with a thickness of 300 mu m were successfully prepared by extrusion at room temperature. After firing at 1400 degrees C, the bare electrolyte micro-tube with a thickness of 210 mu m, a diameter of 3.8 mm, and a length of 40 mm reached a relative density of 96.84% and a flexural strength of 202 MPa. To achieve a better sintering shrinkage match, the electrolyte micro-tubes were pre-sintered at 1100 degrees C, coated with NiO/ScSZ (60 vol.%:40 vol.%) in the inner surface of the microtubes by dip-coating method, and then co-fired at 1400 degrees C. After co-sintering, the interface of the porous anode layer and the dense electrolyte layer demonstrated good adhesion and mechanical integrity. Subsequently, a La0.8Sr0.2MnO3 - delta (LSM)/Ce0.8Gd0.2O2 - delta (GDC) (80 vol.%:20 vol.%) cathode layer was coated on the outer surface of the micro-tubes by dip-coating method and post-sintered at 1100 degrees C. The thicknesses of the anode and cathode layers read approximately 28 and 34 mu m respectively. After thermal cycling between 30 degrees C and 800 C under 97% N-2-3%H-2 on the anode and air on the cathode, the micro T-SOFCs showed no delamination and retained good adhesion based on the SEM results. The maximum power densities (MPD) of the single cell read 0.26 and 0.23 W cm(-2) respectively at 920 and 900 degrees C, and the open circuit voltage (OCV) reported the same 1.08 V. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.