Y.J. Leng

Development of (La, Sr)MnO3-Based cathodes for intermediate temperature solid oxide fuel cells

Conventional (La, Sr)MnO 3 (LSM) electrodes modified by ion impregnation methods showed promising potential as cathodes for intermediate temperature solid oxide fuel cells. After impregnation of ionic conducting-type Gd 0 . 2 Ce 0 . 8 (NO 3 ) x nitrite salt solution into the LSM structure, electrochemical activity of LSM electrodes for the O 2 reduction reaction was substantially enhanced. At 700°C, the electrode polarization resistance of impregnated LSM electrodes decreased to 0.72 Ω cm 2 as compared to 26.4 Ω cm 2 for pure LSM electrodes, a reduction in electrode polarization resistance by 36 times. The polarization losses were also reduced substantially. At 300 mA cm - 2 and 700°C, overpotential for the O 2 reduction was reduced from 0.79 V on pure LSM to 0.19 V on impregnated LSM electrodes, a reduction in overpotential by four times. Ion-impregnated LSM electrodes showed better performance than those of LSM/Y 2 O 3 -ZrO 2 and LSM/(Gd,Ce)O 2 composite electrodes as reported in the literature.

Sinterability and ionic conductivity of coprecipitated Ce0.8Gd0.2O2−δ powders treated via a high-energy ball-milling process

Abstract Ceria-based solid solutions are promising electrolytes for intermediate-temperature, solid oxide fuel cells. The effect of a dry, high-energy, ball-milling process on the sintering and densification behaviour of coprecipitated ceria-based powders is investigated by means of X-ray diffraction, Brunauer–Emmett–Teller (BET) surface-area measurements, density measurements, and electron microscopy. The dry ball-milling process leads to (i) a larger specific surface-area with weak agglomeration; (ii) rearrangement of grains into dense granules; (iii) a higher green density. These effects significantly reduce sintering temperatures and promote densification of ceria-based ceramics. Moreover, a comparison is made of the sintering behaviour and ionic conductivity of the milled samples with and without cobalt oxide doping. Cobalt oxide is a very effective sintering aid, but usually results in an enlarged grain-boundary effect for Si-containing samples. Thus, since SiO 2 is a ubiquitous background impurity in both raw materials and ceramic processing, the dry ball-milling process is a more feasible method for improving the sinterability of coprecipitated ceria-based powders.