Study On The Performance With Bace_0.1fe_0.9-xco_xo_3-δCathode Of Low Temperature SOFCs

Fuel Cells are one of the most promising devices forenvironmentally clean power generation by convertingchemical energy directly into electrical energy.Unfortunately, the traditional SOFCs system limits thecommercial use for the high operating temperature. Thereduction of the working temperature becomes thedirection of SOFCs. IT-SOFCs has become the trend of thefuel cell research,which operating temperature is 500⁸00℃. One major issue is the choice of propercathode which is an important part in fuel cell and itsohmic losses hold about65%of all. In this paperBaCe_0.1Fe_0.9-xCo_xO_3-δ（BCFC,x=0.1⁰.6） composite cathodematerials were synthesized by combined EDTA-citratecomplexing method, and then the structure, morphologyand conductivity were investigated by XRD, SEMtechnology and dc four-point probe method.No anysecondary phase was detected and the single-phaseperovskite was obtained after being calcined at850℃for5h, It further analysis conductivity in the air with theamount of doping change rules of Co. It shows that the conductivityincreases with the content of Co increasing in thetemperature rang from350℃to850℃. Increasing the Cocation doping creates more oxygen vacancies, which isbeneficial to the oxygen reduction reaction,resulting in areduction of the cathode area specific resistance. Thehighest conductivity of8.88S/cm has been achieved at550℃for BaCe_0.1Fe_0.3Co_0.6O_3-δ.The single cell, consisting of a BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ（BZCYYb）-NiO anode substrate, a BZCYYb electrolyte and three different form cathode with pure BaCe0.1Fe0.3Co0.6O3-δ（BCFC）, BCFC-BZCYYb（60%:40%,wt.%） and two layer withBCFC-BZCYYb/BCFC, is assembled and tested from500to650℃with humidified hydrogen as the fuel and the oxygenas the oxidant. The influence of different form cathodematerial composition on the electrochemical performancewere explored.Among all the cell above, the cell with twolayer cathode showed the highest performance which thehigh power densities of139mW cm^-2,179mW cm^-2,223mW cm^-2and276mW cm^-2were obtained at500℃,550℃,600℃and650℃,respectively. The open circuitvoltage of1.185V,1.142V,1.091V and1.043V were achieved. Under the open-circuit condition,thepolarization resistance of the electrode was0.62Ωcm2、0.26Ωcm2、0.11Ωcm2、0.065Ωcm2respectively. It wasfound that I–V and I–P characteristics of the cells withpure BCFC and BCFC-BZCYYb （60%:40%,wt.%） as cathodewere not obviously different，the maximum power densityof135mW cm^-2,149mW cm^-2with the OCV of1.046V,1.026V were obtained at650℃. It is thought that the cell withtwo layers of cathode enlarges the triple phase boundary.With mixed materials as cathode, the electrochemicalactive area was not only in electrode, electrolyte and gasphase three phase boundary, but the entire electrode surface can be used as active area. So the mixture ofmaterial as cathode shows good performance.