Preparation And Characterization Of BaCo_0.7Nb_0.3-xTa_xO_3-? Cathode Materials For SOFC

The Intermediate Temperature Solid Oxide Fuel Cell?IT-SOFC?is a kind of environmentally friendly and efficient all solid state power generation device at600?-800?,which is the main trend of the development of SOFC.The reduction of temperature can reduce the dependence and the cost of cells on materials,prolong the life of cells.However,it also increases the polarization resistance of the electrode.Therefore,finding a cathode material with high oxygen reduction reaction?ORR?catalytic activity at intermediat temperature can improve this problem,which has become a hot topic in the current research.Perovskite type ABO₃ cobalt cathode is a common cathode for IT-SOFC withexcellent catalytic activity and ideal conductivity.When the Ba²⁺of the large radius is completely replaced by the A-site element,the ORR reaction rate of the cathode is accelerated,and the electrochemical performance of the cathode is also improved.However,the structure of the cathodic perovskite phase is unstable,and it is easy to react with the CO₂ in the air.Therefore,this thesis uses the method of co-doping of Nb⁵⁺and Ta⁵⁺with similar ionic radius at the B-site element to improve its performance.In this thesis,we used solid phase method to prepare BaCo_0.7Nb_0.3-xTa_xO_3-??BCNTx,x=0,0.05,0.10,0.15,0.20,0.30?cathode materials and studied its phase structure,microstructure and electrochemical performance.The XRD test results showed that cubic perovskite phase structure had been formed in BCNTx cathode powder after sintering at 1100?for 10 h.Through the AC impedance spectroscopy test of BCNTx/SDC/BCNTx symmetrical half-cells,it can be seen that when sintered at 1000?for 4 h,x=0.10,the polarization impedance Rp of the cathode was minimum,about 0.0495?·cm² at the test temperature of 800?.With Ni_0.9Cu_0.1O_x-SDC as the anode and SDC as the electrolyte BaCo_0.7Nb_0.2Ta_0.1O_3-?as the cathode,we prepared a single cell supported by SDC electrolyte.At 800?,its maximum output power density is 628.51 mW/cm²,and its polarization impedance is about 0.0552?·cm²,indicating that BCNTx is a promising cathode material.