Tae Ho Shin

Layered oxygen-deficient double perovskite as an efficient and stable anode for direct hydrocarbon solid oxide fuel cells

Different layered perovskite-related oxides are known to exhibit important electronic, magnetic and electrochemical properties. Owing to their excellent mixed-ionic and electronic conductivity and fast oxygen kinetics, cation layered double perovskite oxides such as PrBaCo2O5 in particular have exhibited excellent properties as solid oxide fuel cell oxygen electrodes. Here, we show for the first time that related layered materials can be used as high-performance fuel electrodes. Good redox stability with tolerance to coking and sulphur contamination from hydrocarbon fuels is demonstrated for the layered perovskite anode PrBaMn2O5+δ (PBMO). The PBMO anode is fabricated by in situ annealing of Pr0.5Ba0.5MnO3-δ in fuel conditions and actual fuel cell operation is demonstrated. At 800 °C, layered PBMO shows high electrical conductivity of 8.16 S cm(-1) in 5% H2 and demonstrates peak power densities of 1.7 and 1.3 W cm(-2) at 850 °C using humidified hydrogen and propane fuels, respectively.

Doped CeO2-LaFeO3 composite oxide as an active anode for direct hydrocarbon-type solid oxide fuel cells.

Direct utilization of hydrocarbon and other renewable fuels is one of the most important issues concerning solid oxide fuel cells (SOFCs). Mixed ionic and electronic conductors (MIECs) have been explored as anode materials for direct hydrocarbon-type SOFCs. However, electrical conductivity of the most often reported MIEC oxide electrodes is still not satisfactory. As a result, mixed-conducting oxides with high electrical conductivity and catalytic activity are attracting considerable interest as an alternative anode material for noncoke depositing anodes. In this study, we examine the oxide composite Ce(Mn,Fe)O(2)-La(Sr)Fe(Mn)O(3) for use as an oxide anode in direct hydrocarbon-type SOFCs. High performance was demonstrated for this composite oxide anode in direct hydrocarbon-type SOFCs, showing high maximum power density of approximately 1 W cm(-2) at 1073 K when propane and butane were used as fuel. The high power density of the cell results from the high electrical conductivity of the composite oxide in hydrocarbon and the high surface activity in relation to direct hydrocarbon oxidation.

Nano-composite structural Ni-Sn alloy anodes for high performance and durability of direct methane-fueled SOFCs

Ni-based cermets have commonly been used as anode materials with good catalytic properties for hydrocarbon fuels. However, carbon deposition can occur due to the non-ideal electrochemical reaction of hydrocarbon fuel and the structural limitation resulting from the unsymmetrical Ni-based anode-supported single cells. This critical problem leads to loss of cell performance and poor long-term stability of solid oxide fuel cells (SOFCs). Our designed anode material with an extremely small amount (0.5 wt%) of Sn catalyst incorporated into the Ni and nano-composite structure was employed not only to prevent carbon deposition in oxygen deficient areas found for unsymmetrical cells, but also to increase the cell performance due to its excellent microstructure. The nano-composite Sn doped Ni-GDC cells showed a power density of 0.93 W cm−2 with stable operation in dry methane at 650 °C.

Ce0.6 ( Mn0.3Fe0.1 ) O2 as an Oxidation-Tolerant Ceramic Anode for SOFCs Using LaGaO3-Based Oxide Electrolyte

The anodic performance of CeO 2 doped with Mn and Fe was studied by using a Co-doped LaGaO 3 -based oxide (LSGMC) electrolyte. The open-circuit potential approximate to the theoretical value (1.1 V) was exhibited on the cell using Ce(Mn,Fe)O 2 oxide for the anode. A high maximum power density (0.622 W/cm 2 at 1273 K) was attained by co-doping Mn and Fe into CeO 2 . After a few cycles of oxidation treatment at 1073 K, there was an increase in the maximum power density. Therefore, Mn- and Fe-doped CeO 2 is a potential oxidation-tolerant oxide anode for solid oxide fuel cells (SOFCs) using an LSGMC-based electrolyte.

Hierarchically nanoporous La1.7Ca0.3CuO4−δ and La1.7Ca0.3NixCu1−xO4−δ (0.25 ≤ x ≤ 0.75) as potential cathode materials for IT-SOFCs

Hierarchically nanoporous materials based on layered perovskite oxides La1.7Ca0.3NixCu1−xO4−δ (x = 0, 0.25, 0.50 or 0.75) have been synthesized by a facile citrate-modified evaporation-induced self-assembly (EISA) method. These La1.7Ca0.3NixCu1−xO4−δ oxides have been evaluated as potential cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) with Ni–YSZ cermet supported type cells. It was found that La1.7Ca0.3CuO4−δ cathode exhibits the maximum power density at high temperature (e.g., 1.5 W cm−2 at 850 °C), while La1.7Ca0.3Ni0.75Cu0.25O4−δ cathode shows the highest power density at intermediate temperature (e.g. 0.71 W cm−2 at 750 °C) using humidified H2 and air as the fuel and oxidant, respectively. The electrochemical performance of single cells with La1.7Ca0.3Ni0.75Cu0.25O4−δ cathode materials with different morphologies demonstrated better performance in the intermediate temperature range when using the cathode prepared by the citrate-modified EISA method, which has a bigger grain size, but with higher surface area and pore volumes.

Oxide Composite of Ce ( Mn , Fe ) O2 and La ( Sr ) Fe ( Mn ) O3 for Anode of Intermediate Temperature Solid Oxide Fuel Cells Using LaGaO3 Electrolyte

Anodic performance and power generating properties of the cell using various oxide composites consisting of Mn, Fe co-doped CeO 2 and perovskite oxide were investigated by using La 0.8 Sr 0.2 Ga 0.2 Mg 0.15 Co 0.05 O 3 electrolyte. It was found that the theoretical open circuit voltage and reasonably high power density were achieved on the cell using oxide composites consisting of Ce(Mn,Fe)O 2 -La(Sr)Fe(Mn)O 3 for anode. The maximum power density was achieved for values of ~1.0, 0.3, and 0.05 W/cm 2 at 1273, 1073, and 873 K, respectively. Oxidation tolerance was also studied and it was found that the power density was slightly improved after exposure to reoxidation treatment. This study demonstrated that the cell using CeO 2 and LaFeO 3 based oxide composite for anode is highly tolerant against reoxidation treatment. An increase in in the power density by reoxidation treatment was observed and this could be attributed to the improved contact of Ce(Mn,Fe)O 2 -La(Sr)Fe(Mn)O 3 composite powder.

Oxide Composite Anode of Ce0.6Mn0.3Fe0.1O2 and La0.6Sr0.4Fe0.9Mn0.1O3 for Oxidation Tolerant SOFC

Solid oxide fuel cells (SOFCs) are attracting much interest as the efficient generation of electricity and now are closing to a commercial area. At present, the most important subjects for SOFC are increase in reliability as a power generator. For this purpose, development of anode with coke deposition and oxidation is strongly requested. Since Ni based anode is highly active to electrochemical oxidation of fuel, oxidation is easily occurred resulting in deactivation. Therefore, oxidation tolerant anode is strongly requested from reliable cell, however, highly difficult subjects. In this study, we reported the anodic performance of oxide composites consisting of Ce(Mn,Fe)O2-La(Sr)Fe(Mn)O3 for oxidation tolerant SOFC. Development of oxide anode is highly important subject, however development of active oxide anode is rather difficult subjects. Tao et al reported high power density could be achieved by using (La0.75Sr0.25)0.95Cr0.5Mn0.5O3 [1], and we also reported LaMnO3 based oxide anode [2],however, further improvement of power density is requested. Oxide anode of Ce(Mn,Fe)O2 and La(Sr)Fe(Mn)O3 was prepared by using the conventional solid state reaction method at1473 K. Thus obtained powder was mixed in Al2O3 mortal with Al2O3 pestle for 30 min. The electrolyte used for cell test was La0.8Mg0.2Ga0.8Mg0.15 Co0.05O3 (0.25 mm in thickness) prepared by tape casting method. Sm0.5Sr0.5CoO3 prepared by solid state reaction method was used for cathode. Application of anode and cathode on the electrolyte was performed by screen printing method followed by calcination at 1273 K for 30min. Humidified H2 (2.8vol% H2O) and O2 were used for fuel and oxidant, respectively. Figure 1 shows the power generation property of the cell using Ce0.7Mn0.2Fe0.1O2 anode. Evidently, open circuit potential of 1.1V is achieved on the cell at all temperature examined suggesting the high surface activity of this oxide for anodic reaction. The maximum power density is 0.6W/cm2 at 1273 K, which is reasonably high power density reported for oxide anode. Figure 2 shows the power generation property of the cell using Ce0.7Mn0.2Fe0.1O2 anode after exposure to oxygen at 1073 K. In this cell, Sm0.5Sr0.5CoO3 is used for cathode. Evidently, almost theoretical OCV is achieved on all cells and the power density increase upon exposure to the oxidation treatment. This might be explained by the improved contact of ceramic anode. In any case, it is evident that the Ce0.7Mn0.2Fe0.1O2 is promising as the oxide anode for oxidation tolerant SOFC. Since the reasonably high power density was obtained on the cell using Ce0.6Mn0.3Fe0.1O2 and La0.6Sr0.4Fe0.9Mn0.1O3 severally for anode, effects of mixing of both oxides on the power density were studied in this study. Figure 3 shows the maximum power density from 1273 to 773K as a function of Ce0.6Mn0.3Fe0.1O2 content. It was seen that the open circuit potential close to the theoretical value exhibited on the cell using oxide composite at all compositions. On the other hand, the maximum power density is much improved by mixing two oxides and the highest power density is achieved at 75 wt% at 1273 K, however, it becomes maximum at 12.5 wt% Ce0.6Mn0.3Fe0.1O2 at temperature lower than 973 K. Therefore, for intermediate temperature SOFC, 12.5 wt% Ce0.6Mn0.3Fe0.1O2 mixed anode is suitable. The cell using this optimized mixed oxide for anode exhibits the maximum power density of 1000 mW/cm and 23 mW/cm at 1273 and 773 K, respectively. Consequently, this study reveals that oxide Composite Anode of Ce0.6Mn0.3Fe0.1O2 and La0.6Sr0.4Fe0.9Mn0.1O3 is highly promising as oxide anode for IT-SOFC.