Microstructure of LSC Cathodes

In this Section, we demonstrate the effects of controlling the microstructure, and thus pore-size distribution and ohmic resistance, of LSC layers on the enhancement of the electrocatalytic activity.  

The values of 7 lsc are shown in Fig. 12C. While the values of 7 lsc are negligibly small for all specimens at Tceu = 1000 °C, those at Toeii = 900 and 800 °C are almost constant up to 1.0 wt% polymer and increase significantly at 1.5 wt% addition. The steep increase in 7 lsc with increasing pore volume indicates that the electrical contact among LSC particles became worse, which can be correlated to the steep increase in the overpotential 77. 

It is worth discussing the polarization behavior at the LSC cathodes in more detail. Because LSC is a good mixed-conductor at high temperatures. the ERZ is expected to be enlarged over the entire LSC-O2(gas) interfacial area in addition to the TPB as schematically shown in Fig. 13. The oxy gen reduction reaction at the LSC cathode can be envisioned to consist of the following elementary steps. 

Diffusion of OTgas) in gas phase through porous LSC layer 

The surface active sites in the ERZ (denoted as LSC ) play a very important role in the dissociation of O2 molecules to form Oad (step 3 ) and/or in the sequential charge transfer (step 5). The number of LSC sites and their activity strongly depend on the 7 celb gas-diffusion rate, electrode composition, etc. 

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