Study On Normal Impurity’s Effect On Performance Of Proton-conducting Solid Oxide Fuel Cell

Solid oxide fuel cell is the most effective device to convert chemical energy stored byhydrocarbon to electrical energy through electrochemical reaction which is not limitedby Carnot cycle. Being highly efficient and clean, it is a new type of green energy. Itconsists of four parts: anode, electrolyte, cathode and connection material. Currently,operation temperature of normally used cell electrolyte is high which can be above1000°C. How to reduce the operation temperature while obtaining high outputperformance is hot spot of contemporary study. Research shows that some oxides withperovskite structure have high proton conductivity at low temperature （eg.BaCeO3）which can be used as ideal material of cell electrolyte. When cell is in operation, theloss of anode and cathode is small and the polarization loss mainly concentrates oninternal resistance of electrolyte. One effective way to reduce this internal resistanceis to make electrolyte become membrane. Thus some methods to prepare electrolytemembrane are developed in succession, such as spray pyrolysis, laser ablationdeposition, sol-gel, electrochemical vapour deposition, plasma spray, etc. These kindsof preparation processes are high in cost and membrane quality can not be ensured.Dry press, as a traditional ceramic process, is widely applied in laboratories andindustrial production. This method is low in cost, easy to operate and high inutilization ratio of raw material. This paper takes BaZr0.1Ce0.7Y0.2electrolyte which isrelatively stable as the study object. Pechini process is applied to prepare fluffyelectrolyte nanometer powder. Meanwhile, dry press is used to prepare solid oxidefuel cell supported by anode with NiO/BZCY anode as the base. Study shows thatpechini process can effectively reduce the sintering temperature of electrolyte and obtain nanometer power with fine graininess. Impedance spectral measurementindicates that both oxygen conductivity and electron conductivity ofproton-conducting electrolyte are low, meeting the requirement of proton conductorelectrolyte. By fitting Arrhenius curve, it is known that the curve is basically linearwithin measuring temperature range and the conductance activation energy remainsunchanged. This activation energy is0.6826eV. Cell test shows that cell is largelyinfluenced by polarization, much lower than theoretical open-circuit voltage of1.2V.The maximum open-circuit voltage the cell has at700°C reaches0.92V, andmaximum short circuit current density and power density can reach610mA/cm2and140mW/cm2respectively at800°C.When2%、4%of Al2O and SiO2are dopped in electrolyte, elements of Al、Si canreplace part of B atoms and enters the lattice of perovskite structure during electrolytesintering. The shrinkage after sintering is clearly reduced and tightness of compositeelectrolyte has improved. Grain of electrolytes with SiO2is slightly larger than thosewithout dopant while those with Al₂O₃slightly smaller than that without dopant. Asthe increase of doping, the impedance of composite electrolyte becomes substantiallylarge. Cell test shows that composite electrolyte with Al₂O₃can effectively reduce thepolarization loss of voltage. However, both of these two elements can lower theoutput power of cell.