Decreased sintering temperature of anode-supported solid oxide fuel cells with La-doped CeO2 and Sr- and Mg-doped LaGaO3 films by Co addition (original) (raw)
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A high-performance anode-supported SOFC with LDC-LSGM bilayer electrolytes
An anode-supported solid oxide fuel cell ͑SOFC͒ with lanthanum-doped ceria ͑LDC͒ and strontium and magnesium doped lanthanum gallate ͑LSGM͒ bilayer electrolytes was fabricated and tested. The bilayer electrolyte thin film, consisting of a 25 m thick LDC layer and a 75 m thick LSGM layer, was prepared by a simple dry-pressing process. The two electrolyte layers were sintered together well, and no crack and peel-off at the interface were observed. An open-circuit potential of 1.02 V and a maximum power density of over 1.1 W/cm 2 was achieved with H 2 as fuel and air as oxidant at 800°C. The results show that the reactions between LSGM and anode materials were restrained by the LDC electrolyte layer, whereas the electronic conductivity of ceria-based electrolyte was blocked by the LSGM electrolyte layer.
Journal of Power Sources, 2008
La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 2.8 (LSGM8080) powder, showing the highest electrical conductivity among LSGMs of various compositions, is synthesized using the glycine nitrate process (GNP) and used as the electrolyte for an intermediate-temperature solid oxide fuel cell (IT-SOFC). The LDC (Ce 0.55 La 0.45 O 1.775) powder is synthesized by a solid-state reaction and employed as the material for a buffer layer to prevent the reaction between the anode and electrolyte materials. The LDC also serves as the skeleton material for the anode. An anode-supported single cell with an active area of 1 cm 2 is constructed for performance evaluation. A single-cell test is performed at 750 and 800 • C. The maximum power density of the cell 459 and 664 mW cm −2 at 750 and 800 • C, respectively.
Cathode-supported SOFC using a highly conductive lanthanum aluminate-based electrolyte
Solid State Ionics, 2011
A newly-developed, highly conductive, and cost-effective LaAlO 3-based perovskite was used as a solid electrolyte to replace costly LaGaO 3 in this study. The La 0.9 Ba 0.1 Al 0.9 Y 0.1 O 3 (LBAYO) solid electrolyte was fabricated by codoping 10 at.% Ba and 10 at.% Y into the cation sublattice of LaAlO 3. The conductivity of the doubly doped La 0.9 Ba 0.1 Al 0.9 Y 0.1 O 3 was enhanced to 184 × 10 − 4 S cm − 1 which is about 50 times higher than that of the undoped one at 800°C. Cathode-supported cells consisting of Ni/yttria-stabilized zirconia (Ni/YSZ) anode, a thin LBAYO electrolyte (~63 μm), a samarium doped ceria (SDC) interlayer, and a lanthanum strontium manganite (LSM) cathode were assembled and tested. The LBAYO electrolyte film was first prepared on conductive LSM substrates using the electrophoretic deposition (EPD) technique. The cathodesupported structure, consisting of an LBAYO film on a porous LSM substrate, was co-fired at 1450°C for 2 h. A crack-free LBAYO film with a uniform thickness supported on a porous LSM substrate was obtained. Subsequently, a 10 μm-thick SDC buffer interlayer between the electrolyte and 30 μm-thick NiO/YSZ anode was screen-printed and fired on the electrolyte film. A 10-day test showed essentially no degradation on the output power from the cell using the LBAYO electrolyte. These tests convincingly demonstrated the feasibility of an SOFC using LBAYO as the electrolyte when operated at temperatures ranging from 600°C to 800°C.
Electrophretic Deposition of LDC/LSGM/LDC Tri-layers on NiO-YSZ for Anode-supported SOFC
Transactions of the Materials Research Society of Japan, 2010
The SOFC cell composed of an LSGM solid electrolyte and LDC buffer layers was fabricated. The formation of the LDC/LSGM/LDC tri-layer on the NiO-YSZ substrate was performed by a sequential electrophoretic deposition (EPD) technique. The performance of the cells was evaluated at temperatures between 500 and 800 ºC using H 2 and air as the fuel and oxidant, respectively. The cell's open circuit voltage (OCV) of about 0.8V is lower than 1.1V which is the theoretical OCV of the LSGM electrolyte. This suggests that the dense LDC layer may work as the electrolyte in place of the LSGM. It is considered that the microstructure of the LDC buffer layer should be controlled to improve the cell performance.
Innovative processing of dense LSGM electrolytes for IT-SOFC's
Journal of Power Sources, 2006
This paper reports for the first time the attempted synthesis of SrO-and MgO-doped LaGaO 3 (La 1−x Sr x Ga 1−y Mg y O 3−0.5(x+y) , LSGM) perovskite by an aqueous 'regenerative' solution route. This novel technique enabled recycling of the undesired product and subsequently yielded product with much better phase purity and density than that obtained from the solid-state route. La 0.8 Sr 0.2 Ga 0.85 Mg 0.15 O 2.825 (LSGM-2015) and LaGaO 3 were prepared using both the regenerative sol-gel (RSG) and conventional solid-state route at 1400 • C. Series of La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 (LSGM-2017) pellets were also prepared by the RSG method at different sintering temperature (1200-1500 • C) and time. The effect of conventional and microwave sintering of samples obtained from both solid-state and regenerative route was also investigated. Microwave heating was carried out using SiC as a microwave susceptor. The LSGM pellets prepared by using different synthetic methods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and pellet density was determined by pycnometry. The LSGM-2015 prepared by RSG route exhibited conductivity σ t = 0.066 and 0.029 S cm −1 at 800 and 700 • C, respectively, and activation energy of the bulk, grain-boundary, and total are E b = 0.97 eV, E gb = 1.03 eV and E t = 1.01 eV, respectively. The sintering temperature severely affected the grain size (<0.1-10 m) and also the grain-boundary resistance (3-175 k). The unique aspect of this RSG technique is that the final product can be recycled which makes the process cost effective and time saving compared to the solid-state ceramic technique and this technique would allow optimization of processing parameters in a cost effective and time saving manner for obtaining well sintered LSGM as an electrolyte for IT-SOFC's. Published by Elsevier B.V.
Operation of an LSGMC Electrolyte-Supported SOFC with Composite Ceramic Anode and Cathode
Electrochemical and Solid-State Letters, 2007
An all-perovskite-based intermediate-temperature fuel cell was fabricated from materials synthesized using glycine-nitrate process ͑GNP͒ combustion synthesis and modified Pechini synthesis routes. Yttrium-doped strontium titanate ͑SYT͒ was chosen as the conductive ceramic anode component to avoid problems associated with Ni-based anodes. La 0.8 Sr 0.2 Ga 0.8 Mg 0.1 Co 0.1 O 3−␦ electrolyte-supported solid oxide fuel cells ͑SOFCs͒ with composite ceramic anode and cathode exhibit a relatively high power density of 0.246 W/cm at 800°C at 0.5 V.
Effects of a sintering agent for La-doped ceria (LDC) as a buffer layer to prevent a chemical reaction between Ni in anode and Sr-and Mg-doped lanthanum gallate (LSGM) electrolyte during sintering were studied for improving sintering and electrical properties. Electrochemical performance of anode-supported solid oxide fuel cells (SOFCs) using LDC and LSGM films prepared by screen printing and co-sintering (1,350°C) was also investigated. The prepared cell with dense LDC (ca. 17 μm) and LSGM electrolyte (ca. 60 μm) films showed an open circuit voltage close to the theoretical value of 1.10 V and a high maximum power density (0.831 Wcm -2 ) at 700°C. The addition of 1 wt.% LSGM to porous LDC buffer layer was effective for improving the sintering density and electrical conductivity, resulting in the high power density due to the decreased internal resistance loss.
International Journal of Hydrogen Energy, 2010
Transition metal oxides (FeO 1.5 and CoO) were added to Gd-doped ceria (Gd 0.1 Ce 0.9 O 2Àd , GDC) powder for preparing the thin-film electrolyte used in the anode-supported intermediatetemperature solid oxide fuel cell (SOFC). NiOeGDC anode substrate in a weight ratio of 65:35 was fabricated by the tape-casting method. Thin-film electrolyte was fabricated on the presintered anode substrate by screen-printing method and then co-sintered to form the electrolyte/anode bilayer. The cathode, which is made of La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3 and GDC (LSCFeGDC) in a weight ratio of 50:50, was screen-printed on the thus-prepared electrolyte surface and sintered to form a complete single cell. The effects of transition metal oxides on the densification of thin-film GDC electrolyte and on the performance of intermediate-temperature SOFC were studied. Results showed that the densification temperature of thin-film GDC electrolyte could not be further reduced by modifying it with transition metal oxides (FeO 1.5 and CoO) as sintering aids. Both the addition of Fe and Co to GDC enhanced the p-type conductivity of the electrolyte resulting in decreased ohmic resistance. However, they played different effects on the polarization behavior of the cells. Fe-loading decreased the single cell polarization resistance, thus greatly enhancing the charge-transfer process below 600 C. At 500 C, the chargetransfer resistance of the single cell with Fe-loaded GDC electrolyte is only 78% of that of the cell with pure GDC electrolyte. Conversely, Co-loading inhibited the charge-transfer process in the whole testing temperature range. Thus, it can be concluded that Fe-loaded GDC electrolyte is a promising electrolyte material for intermediate-and low-temperature SOFC.
Applicability of La 2Mo 2− y W y O 9 materials as solid electrolyte for SOFCs
Solid State Ionics, 2007
Electrolyte materials with composition La 2 Mo 2−y W y O 9 (y = 0-1.5) exhibit high ionic conductivity ranging from 0.11 S cm − 1 (y = 0) to 0.05 S cm − 1 (y = 1.5) at 1023 K, which is comparable to gadolinia doped ceria. The ionic conductivity is predominant in a wide range of oxygen partial pressures from 0.21 to 10 − 20 atm at 973 K with ionic transport numbers higher than 0.95 under humidified 5%H 2 -Ar. Above this temperature, a significant increase of the n-type electronic conductivity and degradation of the ceramic microstructure are observed as a consequence of the cell volume expansion in addition to the formation of new phases upon reduction. Considering the potential use of these materials as solid electrolytes, the chemical compatibility with most of the typical electrodes commonly used in SOFCs (e.g. cobaltites, ferrites, chromites and manganites) was investigated. Severe chemical reaction was found between La 2 Mo 2−y W y O 9 and most of the studied electrodes, mainly due to molybdenum migration. Furthermore, the high thermal expansion coefficients of La 2 Mo 2 O 9 based materials (∼ 15 · 10 − 6 and ∼20 · 10 − 6 K − 1 in the low and high temperature range, respectively) restrict the choice of compatible materials as cell components. Moreover, electrolyte and electrodes present poor contact due to the low fixing temperature, necessary to prevent excessive chemical reaction between the materials, and also the large thermal expansion coefficients of lanthanum molybdate materials, resulting in the separation of both materials after several consecutive thermal cycles. Therefore, the use of these materials as SOFC electrolyte seems to be rather limited.