Kazunori Adachi

Characterization of solid oxide fuel cell using doped lanthanum gallate

Abstract The power-generation characteristics and the electrode overpotential of the solid oxide fuel cell (SOFC) using doped lanthanum gallate perovskite-type oxide as an electrolyte were measured at temperatures below that of the typical SOFC using yttria-stabilized zirconia (YSZ) as an electrolyte. The oxide ion conductivity of the electrolyte, La 0.8 Sr 0.2 Ga 0.8 Mg 0.15 Co 0.05 O 3− δ (LSGMC), was much higher than that of YSZ. A single cell using LSGMC of 205 μm in thickness showed a power density of 380 mW/cm 2 at a current density of 0.5 A/cm 2 and a temperature of 650°C by using air and dry hydrogen as oxidant and fuel, respectively. The overpotential of anode was larger than that of the cathode and dominated the overall overpotential. The IR-drop measured by current-interrupting method was in good agreement with the value estimated from the electrical conductivity of the electrolyte. The experimental results indicate that LSGMC is a promising material as an electrolyte for a low-temperature SOFC. The characteristics of electrodes are further discussed in terms of the composition and particle size of the starting powders.

Development of a Low Temperature Operation Solid Oxide Fuel Cell

Lowering operation temperature of the solid oxide fuel cell (SOFC) would promote the commercialization of a power-generation module in terms of the manufacturing cost, lifetime, reliability, etc. Mitsubishi Materials Corporation and Oita University have been jointly developing a planar-type SOFC which could operate at a temperature of about 700°C. As an electrolyte, lanthanum gallate (LaGaO 3 ) with substitution of Sr for the La site and Mg and Co for the Ga site was used at this temperature. So far we have established a technique for large-seale cell production, and currently we are examining the performance of a commercial-size cell as large as 154 mm in diam. The obtained cell attained an output power of 31 W with an effective electrode area of 177 cm - at 650°C. Furthermore, a stack of two cells has been tested and the use of stainless steel for the separator was found to be possible during the examined time period at this temperature. The internal CH 4 reforming on the cell has been examined, and the cell output performance using methane [steam/carbon ratio (S/C) = 2] was about 93% of the power density of the cell using hydrogen.

Development of Intermediate-Temperature SOFC Module Using Doped Lanthanum Gallate

An intermediate temperature solid oxide fuel cell (SOFC) module was developed using electrochemically active cells composed of (La, Sr)(Ga, Mg, Co)O 3 electrolyte, Ni-(Ce, Sm)O 2 anode, and (Sm, Sr)CoO 3 cathode. Seal-less planar type stack design was employed. The first generation module successfully provided the output power of I kW with thermal self-sustainability below 800°C. Maximum electrical efficiency obtained with this module was 43%[LHV] together with the corresponding fuel utilization of 78%. Dynamic performance tests demonstrated the capability of output power alteration from 0.6 to 1 kW while maintaining a high electrical conversion efficiency. Further testing and modification of the module for methane fuel utilization are in progress.