In order to fabricate a highly performing cathode for low-temperature type solid oxide fuel cells working at below 700ºC, the cathode modification by samaria-doped ceria (SDC) sol-gel coating was established. The effects of both electrode microstructure control and cathode materials were also studied.
Electrode microstructure control and electrode polarization measurement were performed with an electronic conductor, La0.8Sr0.2MnO3 (LSM) and a mixed conductor, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), Sm0.5Sr0.5CoO3 (SSC). For those cathode materials, when Sm0.2Ce0.8O2 (SDC) buffer layer was formed between the cathode and yttria-stabilized zirconia (YSZ) electrolyte, interfacial reaction products were effectively prevented in the process of cathode sintering at the high temperature and consequently, the electrode polarization was reduced. Moreover, cathode polarization was greatly reduced by applying the SDC sol-gel coating on the cathode pore surface, which can increase triple phase boundary from the electrolyte interface to the electrode surface. For the LSCF cathode with the SDC buffer layer and modified by the SDC sol-gel coating on the cathode pore surface, the cathode resistance was as low as 0.11Ω•cm2 measured at 700ºC in air atmosphere.