作者:
XJ Chen，KA Khor，SH Chan
关键词:
Powders-solid state reaction ； Impedance ； Perovskites ； Fuel cells
摘要:
Oxygen reduction processes at a yttria stabilized zirconia|doped lanthanum manganite (LSM|YSZ) interface are investigated by ac impedance spectroscopy. Three semi-arcs are clearly observed at an oxygen partial pressure ( p O 2 ) of 0.001聽atm. The constant-phase element of frequency arc and the p O 2 -dependence of 1/ R ( R : resistance) are correlated to interpret the reaction processes associated with the frequency arcs. It is found that at least five elementary steps are involved in oxygen reduction at the LSM|YSZ interface. Three of these steps are identified as the rate-determining steps, namely: (i) gas diffusion through the porous LSM electrode from the bulk to the reaction sites; (ii) surface diffusion of oxygen intermediate species along the LSM surface; (iii) incorporation of oxygen ions from the three phase boundary into the YSZ electrolyte lattice. The p O 2 -dependent exchange current density of the rate-determining step predicted by model is consistent with the experimental data, which further confirms the validity of the proposed oxygen reduction processes at the LSM|YSZ interface.
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