Preparation And Properties Of Sm Doped CeO₂ Composite TiO₂ ?Sm Doped CeO₂ Composite Bi₂O₃ Electrolyte Materials

Fuel cell is a device that converts chemical energy into electrical energy directly and efficiently.Solid oxide fuel cell?SOFC?is the most ideal choice for environmental friendly and fuel flexibility of various types of fuel cells.Because of the advantages of all solid state battery components and low operating noise and fast electrode reaction and strong adaptability to fuel,solid oxide fuel cell has been paid more and more attention.In order to achieve the goal of commercialization of SOFC,it is very important to improve the output performance of the medium temperature solid oxide fuel cell,reduce the sintering temperature of the electrolyte and reduce the cost of the battery.At present,the electrolyte materials used in solid oxide fuel cell?SOFC?are mainly YSZ and doped CeO₂ materials.The conductivity of YSZ electrolyte is sufficient only when the operating temperature reached 1000 degrees,so YSZ as the electrolyte of the SOFC operating temperature should be more than 1000 degrees.Such a high operating temperature brings about a series of problems,such as high cost of battery and electrode sintering and difficult selection of connecting materials.Only doped CeO₂ electrolyte can solve the problem of medium temperature and low temperature solid oxide fuel cell,and the conductivity of the doped CeO₂ electrolyte is nearly 1 orders of magnitude higher than that of the YSZ electrolyte in the middle temperature range of 500⁸00 degrees.Doped CeO₂ electrolyte with relatively simple operation and low preparation cost?material content of precious metals is almost zero?.Under the oxygen partial pressure of 10-18 atm,in the case of doped CeO₂ electrolyte,the electron conduction leads to the decrease of the output voltage of the single cell,and then the output power of the battery is reduced,However,CeO₂ is still the most promising medium temperature SOFC electrolyte material.In this paper,CeO₂ based electrolyte is the main research object,the SDC+xmol.%Ti?x=0,0.2,0.4,0.6,0.8,1?electrolyte was prepared by ball milling in solid state method.Phase analysis was carried out by XRD and the morphology was observed by scanning electron microscopy.The distribution of the elements and the atomic ratio were studied by energy analysis.The electrochemical properties were studied by electrochemical impedance spectroscopy?EIS?.The results of XRD show that the SDC – xmol.%Ti electrolyte has a phase of SDC containing cubic fluorite structure in the sintering of 10 hours at a temperature of 1400 degrees.The SEM images show that the grain size of the sample becomes smaller with the increase of the amount of TiO₂,the grain size becomes smaller and the conductivity of grain of the electrolyte becomes larger.But when the amount of TiO₂ is more than the solid solubility,it will gather around the grain to prevent the growth of the grain.You can also slightly increase the Vickers hardness of the electrolyte by adding TiO₂.Electrochemical impedance spectroscopy test showed that when the adding amount of TiO₂ was 0.2mol.% and 0.4mol.%,it can improve the grain conductivity of electrolyte,thereby improving oxygen ion conductivity of the electrolyte to improve output power of a single cell.At 800 degrees,the oxygen ion conductivity of SDC+0.4%mol.%Ti electrolyte will reach to 0.104 S/cm.In this paper,Ni0.9Cu0.1Ox-SDC as the anode and Ba Co0.7Fe0.2Nb0.1O3-? as the cathode make the single cell supported by the electrolyte,and test its output characteristics.Single cell tests show that the open circuit voltage of each of the samples are decreased with the increase of the temperature,the power density of samples are increased with the increase of the temperature,the cell supported by the SDC+0.4 mol.%Ti electrolyte shows the best performance,the maximum power density of all of the single batteries supported by the electrolyte can reach 0.507 Wcm^-2 at 800 degrees.Ce_0.8Sm_0.2O_1.9+xmol Bi?x=0,0.05,0.1,0.15,0.2?electrolyte is prepared by glycine-nitrate method.It is Sm doped CeO₂ composite Bi₂O₃ obtaines the Ce_0.8Sm_0.2O_1.9+xmol Bi electrolyte that can form a better electrolyte film by sintering at 1100 degrees for 5 hours.Phase analysis was carried out by XRD and the morphology was observed by scanning electron microscopy.The distribution of the elements and the atomic ratio were studied by energy analysis.The electrochemical properties were studied by electrochemical impedance spectroscopy?EIS?.XRD results show that the Ce_0.8Sm_0.2O_1.9+xmol Bi electrolyte sintered at 1100 degrees for 5 hours,when x=0,0.05,0.1,the electrolytes contain only the cubic fluorite structure of SDC phase,no other phases generate;when x=0.15 and 0.2,the electrolyte will grow impurity phase Bi₂O₃.The SEM photos of the electrolyte can be seen that the average particle size of the electrolyte sintered at 1100 degrees for 5 hours is relatively small,at x=0.15 and 0.2,some small crystalline Bi₂O₃ appear on the SBDC electrolyte.EDX analysis can be seen that a small amount of Bi doped still accord with the original design of the atomic ratio.The hardnesses of SDC electrolyte obtained by Sm doped CeO₂ composite Bi₂O₃ have exceeded the hardnesses of SDC themselves,especially the hardnesses of the Ce_0.8Sm_0.2O_1.9+0.1mol Bi electrolyte can reach to 866.8 Hv.The oxygen ion conductivity of the Ce_0.8Sm_0.2O_1.9+0.1mol Bi electrolyte can reach 0.114 S/cm by AC impedance spectroscopy.