| Intermediate temperature (≤800℃) solid oxide fuel cells (IT-SOFCs) are highly efficient and environmentally friendly devices to convert chemical energy to electrical power directly. Cathode always plays a vital role in the improvement of the output performance of fuel cells. Therefore, it is critical to exploit cathode materials with superior catalytic activity for IT-SOFC.A nano-structure cathode is beneficial to achieving high electrocatalytic activity and large triple phase boundary (TPB) length where oxygen reduction reaction takes place. Cobalt-based oxides Ca3Co4O9-δ(CCO) and CCO-Ag nanocomposite were synthesized and investigated as potential cathode materials for IT-SOFC based on Sm0.2Ce0.8O1.9 (SDC) electrolytes. Both of the cathodes were prepared by screen-printing and ion impregnation techniques. The electrochemical performance was determined from 600℃ to 800℃ and the expected results were obtained.CCO nanoparticles were impregnated into the porous and pre-sintered SDC backbones that were screen-printed onto the dense SDC substrate, repeated the impregnation process to increase the amount of CCO nanoparticles. Interfacial polarization resistances (Rp) were measured on symmetric cells CCO/SDC/CCO with four-electrode configuration using AC impedance spectroscopy. At 800℃, the Rp of CCO cathode reaches the lowest value of 0.202 Ω·cm2, the maximum power density of the electrolyte-supported single cell Cu0.1Ni0.9-SDC/SDC/CCO with the nano-structured cathode was as high as 489.5 mW·cm-2.Nanosized Ag particles were infiltrated into CCO cathode by impregnating AgNO3 solution to improve the electrode performance, a CCO-Ag nanocomposite electrode was fabricated. The composite cathodes showed the best performance when the impregnation treatment was repeated for 5 times, the Rp decreased by 33.36% at 800℃ from 0.202 Ω·cm2 (CCO) to 0.1346 Ω·cm2. The Ag impregnated cell exhibited a peak power density of 487.1 mW·cm-2. |
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