Anode Materials for SOFCs

The deposited carbon not only may block the porosity of the anode but also disrupts the cermet microstructure, breaking Ni-ZSZ linkages, and finally causes degradation of cell performance. 

Mixed metal oxides have been targeted as possible alternatives they are potentially less likely to promote carbon buildup, due to the higher availabihty of oxygen throughout the anode (Fig. 8.1), and are less likely to suffer from sulfur poisoning [12]. 

The challenge is to develop a single-phase oxide material that catalyzes fuel oxidation, reduces significantly the problems described above, and possesses a level of mixed electronic ionic conductivity comparable with the nickel YSZ cermet. 

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Zha S, Cheng Z, and Liu M. A sulfur-tolerant anode materials for SOFCs GdjTij 4Mo06O7. Electrochem Solid-State Lett 2005 8 A406-A408. 

Another way to decrease the anodic overpotential is to intercalate a mixed conductor between the yttria stabilized zirconia electrolyte and the metallic anode. Such a combination enlarges the reaction area which theoretically lowers the anodic overpotential. Tedmon et al. [93] pointed out a significant decrease of polarization when ceria-based solid solutions like (Ce02)o.6 (LaO, 5)04 are used as anode materials for SOFCs. This effect is generally attributed to the mixed conductivity resulting from the partial reduction of Ce4+ to Ce3+ in the reducing fuel atmosphere. A similar behaviour was observed in water vapor electrolysis at high temperature when the surface zirconia electrolyte is doped with ceria [94, 95]. 

Since ionic radii and valences of iron and chromium ions are similar to gallium ion, substitution of these cations with gallium ion may result in powders with similar crystal structure and properties to LSGM. Moreover, LaFe03- and LaCr03-based oxides are candidate cathode and anode materials for SOFC, respectively. 

Back in 1964, Mobius and Rohland showed that ceria could work as an anode in an SOFC fuelled with H2 and CO, and shortly after Takahashi cl al. described C(,6Yo40iji and CCq6 30 40) ft as being excellent anode materials for SOFC. Since Ihen, a number of studies have been carried Cells with a ceria anode may... 

Cheng Z et al (2011) From Ni-YSZ to sulfur-tolerant anode materials for SOFCs electrochemical behavior, in situ characterization, modeling, and future perspectives. Energy Environ Sci 4 4380... 

Zha SW, Cheng Z, Liu ML (2005) A sulfur-tolcaant anode material for SOFCs Gd2Xi1.4Moo.6O7. Electrochem Solid State Lett 8 A406-A408... 

General While Ni/YSZ cermet is the most preferred anode material for SOFCs operating with hydrogen-containing fuels, there are several efforts to find alternative materials for the SOFC anode. Many studies on oxide anodes have been made for perovskite-related oxides. LaCr03 [230-237], LaFeOs [238], LaTiOs [239], and SrTiOs [240-243] systems are considered as possible alternative anode materials. 

Although a wide range of materials has been considered as anode materials for SOFC (14), most developers today use a cermet of nickel and YSZ. Early on in the development of SOFC, precious metals such as platinum and gold were used, as well as pure transition metals such as nickel and iron. Because of the physical and chemical instability of these materials, other materials such as nickel aluminide were tested. 

C., and Irvine, J.T.S. (2008) Ce-Substituted LSCM as new anode material for SOFC operating under dry methane. Solid State Ionics, 179,1562 1566. 

Dongare, M.K., Dongare, A.M., Tare, V.B., and Kemnitz, E. (2002) Synthesis and characterization of copper-stabilized zirconia as an anode material for SOFC. Solid State Ionics, 152-153, 455-462. 

In recent reviews by Goodenough and Huang (2007) and Sun and Stimming (2007), advances in alternative anode materials for SOFCs are described. 

Sauvet, A.-L. and Irvine, J.T.S. Catalytic and electrocatalytic studies of new type of anode materials for SOFC under methane. In Proceeding of the 5thEuropeanSolidOxide Fuel Cell Forum Huijsmans, J., Ed. Switzerland, 2002, pp. 490 98. 

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