Preparation And Performance Researches Of Ce-(1-x)Sm_xO_2-δ Electrolyte And NiO/SDC Composite Anode

Fuel cells are a device which can convert energy with high efficiency andlow pollution. They are also called cells because they are composed of cathode,anode and electrolyte sandwiched by them, which are the same with thetraditional cell, But they produce electricity by electrochemical combination offuel gas (e.g. hydrogen) with oxidant gas (e.g. oxygen),which differs from thetraditional cell used to reserve energy. So they can also be looked as a generatorwith an electrochemical process. But compared with the conventional generatorwhose efficiency of producing electricity, they are not subject to the Carnot 3limitation, they convert the chemical energy directly to electrical energy withoutintermediate of thermal energy and have excellent energy conversionefficiency as a result. In addition to high efficiency and low emissions, they havealso several other advantages such as modular and distributed nature, and muchlower production of pollutants. Since fuel cells just have these advantages, theywill play an essential role in any future hydrogen fuel economy. As the forthgeneration fuel cell, SOFCs (Solid Oxide Fuel Cells)hasseveral outstanding advantages: Because all the components of SOFCs ar e solid,they can be fabricated in very thin layers and configured into uni- que shapesunachievable in other fuel cells systems having a liquid electr- olyte. Thesefeature permit themdesign with additionalperformance imp- rovement;moreover, SOFCs offer good fuel flexibility, they can use the H2, CO as well asthe natural gas﹑ coal gas turns spirit and other carbon hydrogencompounds asfuel materials. During SOFC operating, they are unnecessary to use preciousmetals as the catalyst, so the cost of them can be minimized, the efficiency of theoverallenergyconversion efficiency can attain 80% above. the development of SOFCs attractsthe interests all over the world because of these merits. Today's demonstration SOFCs utilize yttria stabilized zirconia(YSZ)containing typically mol%Y, as the electrolyte; a ceramic-mentalcomposite(cermet) comprised of Ni+YSZ as the anode; and La1-xSrxMnO3-δ,(lanthanum strontium manganite or LSM)as the cathode,in general, they mustoperate at high temperature because of the low ionic conductivity of YSZelectrolyte at lower operating temperatures, such high operating temperaturescause many serious problems such as physical and chemical degradation of the 4SOFCs component materials. Therefore, it is important to reduce the operationtemperature of SOFCs, it is desirable to develop the new electrolyte operating atthe Intermediate-Temperature(IT) and the electrode materials which match with itmutually. According to these, in this thesis, bases on study of synthesis andperformance of Ce1-xSmxO2-δ(x=0.05,0.1,0.15,0.2,0.3),we adopted the meansof optimization to go together with ratio, the NiO/SDC composite anodematerials were synthesized by using the traditional method. The properties of thesynthesized products were studied in detail using XRD spectra﹑　a.c. impedancespectra and electrochemical analysis: (1) A series of Ce1-xSmxO2-δ(x=0.05,0.1,0.15,0.2,0.3) electrolyte weresynthesized by Sol-Gel method. By the measurements of their physical propertiessuch as crystal structure﹑　a.c. impedance spectra and thermal expansion, theirdifferences in micro-mechanism were compared and discussed. The results of theresearch show that Ce1-xSmxO2-δ(x=0.05～0.3) electrolyte are single phase solidsolutions with fluorite structure at 1300℃,which is much lower than thetemperature of using solid state method:　1600℃-1650℃；moreover,　Ｃｅ０．８５Ｓｍ０．１５Ｏ２－δ　has the highest conductivity of 0.092S/cm and the lowest activation energy of0.742 eV at 800℃. (2) Several NiO/SDC composite anode with different NiO contents weresynthesized by mechanic...