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Intermediate Temperature SOFCs

We have already discussed some materials that could be used as low-temperature SOFC electrolytes. Referring again to Figme 7.22, if we assume that the electrolyte should not contribute more than 0.15 Vcm to the total cell area specific resistance, then for a thickness (L) of 15tim, the associated specific ionic conductivity (a) of the electrolyte should exceed 10 Scm (since a = L/ASR = 0.0015/0.15). [Pg.225]

Clearly, ytfria-stabilised zirconia has sufficient ionic conductivity to meet the target at around 700°C, and for ceria-gadolinium oxide (CGO) the temperature is around 500°C. This assumes that elecfrolytes as thin as 15 p.m can of course be made. In fact, such thin films can be made by a variety of techniques, but because the material is so fragile it is necessary to provide support for the electrolyte in such cells. In other words, the thin electrolyte does not have the mechanical strength to support the electrodes as is the case with conventional high-temperature planar SOFCs. Most manufacturers have opted for supporting the elecfrolyte on relatively thick anodes, and these are often referred to [Pg.225]

One of the problems with anode-supported cells is that any difference in thermal expansion between anode and electrolyte becomes more significant than in conventional high-temperature SOFCs. For this reason many developers use porous nickel cermet anodes with interfacial regions made of NiA SZ doped with ceria. Operating at temperatures below about 700°C means that metallic bipolar plates can be used, and the lower the temperature, the less exotic the steel needs to be. Ferritic stainless steels can be used below about 600°C, and these have the advantage that they have a low thermal expansion coefficient. Conventional doped LSM-YSZ cathodes can be used but there is much development in progress to improve cathode materials as the cathode overpotentials become more significant as the cell temperatures are lowered. A recent review of cathode materials has been published by Ralph (2001). [Pg.226]

The search for new materials for IT-SOFCs is currently a key activity. Ceria materials, as noted earlier, are more conductive than the traditional YSZ except that ceria is unstable at elevated temperatures in reducing atmospheres. Fortunately, if the temperature of operation is as low as 500°C, then the increased electronic conductivity caused by reduction of to Ce + ions is relatively low and then this issue appears not to be such a big concern (Steele, 2001). Lanthanum gallate electrolytes are also being investigated for IT-SOFC applications, and time will tell which material offers the best prospects, both technically and economically, for conunercial systems. [Pg.226]

Appleby J. (1984) in Proceedings of the Workshop on the Electrochemistry of Carbon, S. Sarangapani, J.R. Akridge, and B. Schunun (eds) The Electrochemical Society, Pennington, NJ, p. 251. [Pg.226]


It was also found [8] that the sintering conditions have significant effects on the resistivity of the Smo.iCeo.gOi.g material. As shown in Fig. 4, the overall resistivity decreases with lower sintering temperature and attains a minimum at the sintering temperature of 1100-1200 °C, which is about 31 ohm-cm at 700 °C measurement. This makes the Smo.2Ceo.801,9 material capable of working as SOFC s electrolyte at temperatures lower than 700 C to avoid possible reduction of cerium (4+) and thus suitable for intermediate-temperature SOFC. [Pg.98]

An alternative to the Co-rich perovskites is the Sr-doped LaFe03 which has a lower thermal expansion coefficient and a superior chemical compatibility with doped Ce02 electrolyte. LaFe03 is expected to be more stable than Ni- and Co-based perovskites because the Fe3+ ion has the stable electronic configuration 3d5. It is, therefore, expected that compositions in the system (La,Sr)(Co,Fe)03 will have desirable properties for intermediate temperature SOFC cathode applications. [Pg.147]

Misono T, Murat, K, Fukui T, Chaichanawong J, Sato K, Abe H et al. Ni-SDC cermet anode fabricated from NiO-SDC composite powder for intermediate temperature SOFC. J. Power Sources 2006 157 754—757. [Pg.278]

Li Q, Zhao H, Huo L, Sun L, Cheng X, and Grenier JC. Electrode properties of Sr doped La2Cu04 as new cathode material for intermediate-temperature SOFCs. Electrochem. Commun. 2007 9 1508-1512. [Pg.279]

Fu C, Sun K, Zhang N, Chen X, and Zhou D. Electrochemical characteristics of LSCF-SDC composite cathode for intermediate temperature SOFC. Electrochim. Acta 2007 52 4589-4594. [Pg.279]

Liu Y, Compson C, and Liu M. Nanostructured and functionally graded cathodes for intermediate-temperature SOFCs. Fuel Cells Bull. 2004 10 12-15. [Pg.281]

Ma XQ, Hui S, Zhang H, Dai J, Roth J, Xiao TD et al. Intermediate temperature SOFC based on fully integrated plasma sprayed components. In Thermal Spray 2003 Advancing the Science Applying the Technology, C. Moreau and B. Marple (eds.) 2003 Materials Park, Ohio ASM International. [Pg.281]

Given the large number of potential beneficial effects of lowering the nominal operating temperature of the SOFC stack and their corollary affect on system cost, intermediate temperature SOFC concepts are being pursued by many organizations throughout the U.S. and the World. [Pg.172]

Chiba, R., Yoshimura, F., Sakurai, Y., Tabata, Y., and Arakawa, M. A Study of Cathode Materials for Intermediate Temperature SOFCs Prepared by the Sol-gel Method, Solid State Ionics, 175,23 (2004). [Pg.133]

The intermediate temperature SOFC offers an advantage over the PEM cell of a predicted higher efficiency, 45-50% compared to 30%. It can also be integrated with a reformer which, utilizing some of the waste heat, produces useable fuels, (H2 and CO) from a hydrocarbon fuel. [Pg.195]

Mixed-conducting (A,Ln)M03 (M = Fe, Co), promising as cathodes of intermediate-temperature SOFCs, oxygen-separation membranes, and electrocatalysts for high- and low-temperature processes involving oxygen. [Pg.491]

However, 1000 °C leads to a very rapid reaction if anode reform is attempted and in many cases the result is excessive thermal stress of the ceramic electrolyte, so that conventional reformers must be used. As a consequence there has come about a class of intermediate-temperature SOFCs based on alternative ceramic formulations, 500 °C operation having been achieved by a metal/ceramic fuel cell by the company Ceres (see Chapter 4) set up by Imperial College London. [Pg.35]

MCFCs and intermediate-temperature SOFCs can incorporate catalysed reform at their anodes, where the hydrogen electrochemical oxidation proceeds simultaneously, and heats the non-Faradaic and endothermic reform and shift reactions The latter process is immediately superior to a separate reformer, because it eliminates combustion reaction irreversibility. Heat produced at such an anode is given, in Appendix A, the title reversible heat , that is heat produced without the thermal degradation which occurs in the combustion reaction. [Pg.60]

At 600 °C in the MCFC, the dynamic equilibrium conditions are ideal for anode reform. The voracious oxidation reaction swallows both reform and shift reaction products as they are formed. The latter reactions are left striving to equilibrate. In the high-temperature SOFC the reform reaction is very vigorous, and uneven temperature distribution can occur. To avoid that irreversibility, Siemens Westinghouse still employs separate reformers. More irreversibility, but SOFC temperatures are on their way down The intermediate-temperature SOFC is emerging. [Pg.60]

Long-term successful operation of the SOFCs requires that the electrolyte possess adequate chemical and structural stability over a wide range of oxygen partial pressures, from air or oxygen to humidified hydrogen or hydrocarbons. The requirements for the electrolyte used in the intermediate-temperature SOFCs (IT SOFCs) include ... [Pg.211]

L.-W. Tai, M.M. Nasrallah and H.U. Anderson, Lai-xSrxCoi-yFeyOs-a, A potential cathode for intermediate temperature SOFC applications, in S.C. Singhal and H. Iwahara (Eds.), Proceedings of the 3rd International Symposium on Solid Oxide Fuel Cells. The Electrochemical Society, Pennington, NJ, 1994, pp. 241-251. [Pg.525]

PERFORMANCE OF ELECTROLYTE SUPPORTED CELL Above results, lOSclCeSZ is expected to be the good material for SOFC application. The electrolyte supported Cell (ESC) using lOSclCeSZ for intermediate temperature SOFC was developed in this study. We have studied various electrode materials to match the lOSclCeSZ electrolyte and find that the specifications in Table 1 show good cell performance. [Pg.187]

Key words Zirconia/Ceria/Lanthanum GaUate/Intermediate Temperature/SOFC... [Pg.21]

The highest values of approximately 20 Q cm were obtained for the commercial alloy 1.4742 which has in some cases been considered as a potential candidate to be used as interconnect in intermediate temperature SOFCs. These high values can be explained by the fact that this alloy, depending on the exact alloy composition and surface treatment, in some cases tends to form a veiy protective alumina scale [5], which, however, possesses a very poor electrical conductivity. In contrast, the new JS-3 alloys (batches JDA, JEW, and JEX) show very low contact resistance values of approximately 10 mf2cm, i.e., values which are two to three orders of magnitude smaller than those of most commercial alloys. [Pg.101]

After the loss due to grain boundaries in the electrolyte is minimized, probably we shall be able to produce an efficient electrolyte with a higher electroconductivity for use in intermediate-temperature SOFC s. [Pg.270]


See other pages where Intermediate Temperature SOFCs is mentioned: [Pg.97]    [Pg.3]    [Pg.8]    [Pg.13]    [Pg.64]    [Pg.132]    [Pg.180]    [Pg.9]    [Pg.148]    [Pg.47]    [Pg.1547]    [Pg.167]    [Pg.243]    [Pg.220]    [Pg.191]    [Pg.102]    [Pg.21]    [Pg.22]    [Pg.23]    [Pg.25]    [Pg.27]    [Pg.29]    [Pg.31]    [Pg.33]    [Pg.35]    [Pg.74]    [Pg.237]    [Pg.47]   


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