Study On Composite Electrolyte And Cathode Materials For Low Temperature Solid Oxide Fuel Cells

As a promising energy-conversion device, solid oxide fuel cell(SOFC)possessing many notable advantages, such as high efficiency, environmental friendly and flexibility of fuels has received a great attention in recent years. However, the high operation temperature limits its application. So lowering the operation temperature becomes one of the hot topics. However, lower operation temperature brings more challenges to an electrolyte on its electrical conductivity, and to cathode materials on their catalytic activity. In this paper, the effects of(1) carbonate addition on the conductivity of Sm0.2Ce0.8O1.9(SDC)-carbonate composite electrolyte and(2)Ag content on the catalytic ability of Pr2NiO4(PNO)-Ag composite cathode were well-investigated.SDC was synthesized by coprecipitation then composited with different contents of(Li/Na)2CO3(molar ratio of Li: Na= 52: 48) to prepared composite electrolytes with different carbonate contents. The addition of carbonate could promote the material electrical conductivity, suppress the growing of SDC and lowing the sintering temperature. Among the SDC-carbonate, the material with 20 wt% carbonate shows the best microstructure, electrical conductivity(0.51 S cm-1at 575oC) and power output performance. The single cell with it as electrolyte got a maximum power density of approximate 700 mW cm-2 at 600 oC.A precursor of Pr2NiO4(PNO) was prepared by coprecipitation. It was then calcined under three different conditions, 1000 oC for 3 h, 1000 oC for 5 h and 1200 oC for 5 h. respectively. The XRD demonstrates only the sample calcinating at 1200 oC for 5h is in line with the standard K2NiF4 crystal type, while the other two contain impurity of Pr6O11. PNO-Ag composites were synthesized by Impregnation, Solid phase transformation and Freeze-drying method, respectively. The resulted PNO-Ag composites by impregnation method comparatively has the smallest particle, the least agglomeration as well as the most uniform Ag particle size. Its cathodic area specific resistance(ASR) by EIS is the lowest to be only 1.24 ??cm2 at 600 oC. In addition,the effects of Ag deposition amount on its cathodic ability were investigated. The ASR firstly decreases then increases with the increase of Ag content. The sample with15 wt% Ag deposition performsthe lowest ASR of only 0.45 ??cm2 at 600 oC,indicating PNO-Ag with 15 wt% Ag deposition possesses the best cathodic catalytic performance for oxygen reduction. A maximum power density of 710 mW cm-2was achieved at 600 oC.