| Engery and environmental issues have become major challenges that the humansociety is now facing for the sustainable development. Solid oxide fuel cell (SOFC) isan electrochemical device that convert chemical energy dircectly into electrical energy,has received worldwide attention for its high conversion efficiency, low pollutant levels,excellent fuel adaptability and so on. A traditional SOFC consists of a dense electrolytesandwiched by porous anode and cathode.Traditional SOFC utilize Y2O3stabled ZrO2（YSZ）as electrolyte and operate at hightemperatures between800℃and1000℃. This kind of SOFC is called as hightemperature solid oxide fuel cell (HT-SOFC). However, such high temperature mayresult in many serious problems, such as high fabrication cost, interfacial diffusionbetween electrolyte and electrodes, easy material aging under the high temperature, anddifficulties in choosing sealing and bonding materials, etc. These problems seriouslyhindered the commercial development of SOFC. Therefore, intermediate-temperaturesolid oxide fuel cell (IT-SOFC) has attracted attention of reseaechers around the world.However, a lower operating temperature will lead to a loss of output power density dueto significant reduction in both ionic conductivity of the electrolyte and catalyticactivity of the electrodes. In order to develop IT-SOFC with satisfactory performance,the solid electrolyte material and the electrodes working at the IT region are importantfor determining the performance of IT-SOFC.There are two considerable solutions to develop the performance of the solidelectrolyte. One is to look for a solid electrolyte material with high conductivity at ITregion. The other one is to reduce the thickness of the electrolyte into micrometric scale.Electrolyte film may observably reduce the internal resistance and power loss ofIT-SOFC. However, as the operating temperature decreases, the polarization resistance between electrodes and electrolyte increases rapidly. And the polarization resistancebetween electrolyte and cathode becomes the limiting factor in the performance of thecell. Therefore, the cathode material is one of the most important objects of study onIT-SOFC.Based on the above, this paper focused on the performances of IT-SOFC based onproton-conducting electrolyte membrane and novel cathodes. Main works and results ofthis paper are as follows:A novel series of cobalt-free perovskite oxides La0.6Sr0.4Fe1-xNbxO3-(0.00≤x≤0.20)were prepared by a solid state reaction method, the La0.6Sr0.4Fe0.9Nb0.1O3-(LSFN10)was investigated as a potential cathode material for proton-conducting IT-SOFC. Theconductivities of La0.6Sr0.4Fe1-xNbxO3-(0.00≤x≤0.15) ceramic pellets weredetermined by impedance spectrometry as functions of temperature (300-800℃). ANiO-BaZr0.1Ce0.7Y0.2O3-(BZCY) composite anode-supported proton-conducting BZCYelectrolyte membrane was successfully fabricated by a simple, cost-effective spincoating process. And then, the cathode slurry was painted on the BZCY electrolytemembrane of the half cell to obtain the single cell (NiO-BZCY|BZCY|LSFN10). Thecell was tested from500℃to700℃with H2as fuel and air as oxidant, respectively.The overall conductivities of the samples increase with increasing temperature. It isattributed to a semiconductor-like conduction behavior of the samples at the giventemperature region. The conductivity of LSFN10increases with the increasing pO2inthe oxygen partial pressure range of10-10-1atm, indicating the p-type conduction in thesample is dominant. The peak power density of the cell reached503mW·cm-2at700℃,and the interfacial polarization resistance (Rp) was as low as0.17Ω·cm2at the sametemperature.In this paper, a new series of cobalt-free perovskite oxides La0.6Sr0.4Fe1-xMoxO3-(0.00≤x≤0.20) were prepared by a citric acid-nitrate process. The conductivities of theseries of La0.6Sr0.4Fe1-xNbxO3-(0.00≤x≤0.15) samples were determined by impedancespectrometry as functions of temperaturefrom300℃to800℃. Among these ceramicsamples, the La0.6Sr0.4Fe0.9Mo0.1O3-(LSFM10) sample has the highest conductivity tobe159S·cm-1in air at475℃. The single cell of NiO-BZCY|BZCY|LSFM10wassuccessfully fabricated and tested at500-700oC using hydrogen as fuel and air asoxidant. The peak power density and the interfacial polarization resistance (Rp) of thefuel cell were496mW·cm-2and0.15Ω·cm2at700℃, respectively. In conclusion, these results above show that the cobalt-free perovskite oxidesLa0.6Sr0.4Fe0.9Nb0.1O3-and La0.6Sr0.4Fe0.9Mo0.1O3-are both promising cathodematerials for proton-conducting IT-SOFC. |
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