| A fuel cell is a device that can convert chemical energy into electricity directly. The fuel cell is also called a cell because it is composed of electrolyte, anode and cathode, which are the same for a normal cell. The fuel cell generates electricity is the fourth generation technique after the hydraulic power, thermal power and the atomic energy. Theoretically, As long as continue to supply the fuel, the fuel cell can continue to generate electricity then. It generates electricity from fuels such as hydrogen, natural gas and other hydrocarbons. It is Different from traditional cells that can only reserve energy; fuel cell can convert energy continuously. Because it is not limited by the Carnot cycle, fuel cell has advantages of higher energy conversion efficiency and lower polluted gases emission than the traditional generator. With the natural resource exhaustion and environment deterioration, developing efficient and environmental friendly energy techniques is necessary recently. Since fuel cell just matches such requirements, it attracts the interest all over the world.As the fourth generation fuel cell, SOFC (Solid Oxide Fuel Cell) has many outstanding advantages. First, with all solid components, SOFC eliminates problems liquid electrolyte fuel cell faces, such as corrosion and leakage of liquid electrolytes. Second, operating at high temperatures, its electrode reaction is so fast that it is unnecessary to use noble metals as electrodes. Thus the cost of cells can be minimized.At the same time, the high quality heat it emits can be fully used. The overall energy conversion efficiency of the thermal-electric system can be added up to 80%. The most outstanding advantage of SOFC is that it can use a large of different fuels, from the hydrogen, carbon monoxide to the natural gas, even other combustive gases. The main difficulty the SOFC faces currently is the problem caused by high temperature and the ceramic components'match.As the central component, the electrolyte affects the performance of a SOFC directly. The electrolyte of a SOFC must have adequate oxygen ion conductivity, stability at both oxidizing and reducing atmospheres, enough hardness and toughness and low costs. Today's demonstration SOFCs utilize yttria stabilized zirconia(YSZ) containing typically 8mol%Y, as the electrolyte,in general, they must operate at high temperature because of the low ionic conductivity of YSZ electrolyte at lower operating temperatures, such high operating temperatures cause many serious problems such as physical and chemical degradation of the SOFCs component materials. Therefore, it is important to reduce the operation temperature of SOFCs, it is desirable to develop the new electrolyte operating at the Intermediate-Temperature (IT) and the electrode materials that match with it mutually. one path is to make the electrolyte of YSZ into thin film, another is to look for a new electrolyte that work in intermedium-temperature area(600℃-800℃). Because the thin film technique cost is high,craft complicacy , So the second path most contain attraction, Recently, intermedium- temperatures (600℃-800℃) SOFC (IT-SOFC) has received much interest because a replacement of YSZ by a reduced-temperature oxygen-ion conductor in SOFCs would greatly reduce material and fabrication problems and improved cell reliability during prolonged operation. So exploring new type of electrolyte and electrode and their synthesis method is very important for developing IT-SOFC.Now, Ceria-based electrolytes are noteworthy as candidates for electrolyte materials. because this material contains the electronics conductivity , so make open circuit voltage(OCV)and exportation power of the fuel cell lowered. We can make it into composite material that increases the various functions of CeO2.The electrolytes materials Ce0.85Sm0.15O1.92(5SDC)were synthesized by means of glycine-nitrate process(GNP)and BaCe0.8Y0.2O3-δ(BCY20) were synthesized by means of a Pechini method process then the composite electrolytes were prepared by mixing SDC and BCY20(the weight ratio between SDC powder and BCY20 powder were 85∶15 , 75:25 , 65∶35, respectively ) Its phase composition and micromorphology were investigated by XRD and SEM.Its electrical properties were investigated by direct current and impedance spectroscopy in air. It shows that when the composition was 85wt.%SDC and 15wt.% BCY20 (SB8515), the electrolyte has higher electrical conductivity as compared to SDC in the temperature of 400-750 oC. Electrolyte-supported solid oxide fuel cells (SOFC) were fabricated with NiO/SDC as the anode and Ba0.5Sr0.5Co0.8Fe0.2O3-δas the cathode. The V-I characteristics of single cell shows that output power density for the cell with SB8515 and SB7525 as electrolyte higher than for the cell with SDC and BCY20 as electrolyte at 750 oC .The open circuit voltage(OCV)of the cell using the composite electrolytes was higher than the cell using single SDC as electrolyte at the working temperature (600-800 oC).In sum , CeO2-based as the main object of study in this paper, which make use of composite materials design idea to explore to enhance its ion conductivity and reduce the electronic conductivity of CeO2-based electrolyte and The ultimate goal to improve the SOFC performance.
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