Preparation And Properties Of Corrosion-resistant Barium Ceria-based Composite Electrolytes

BaCeO₃with perovskite structure has attracted much attention because of its excellent electrical conductivity as electrolyte for intermediary temperature（500-800°C）solid oxide fuel cells.However,its poor corrosion resistance in CO₂and water vapor atmosphere limits its practical application.In order to solve this problem,on the one hand,the main phase grain properties are improved and the grain boundary properties are regulated by composite modification,so as to improve the corrosion resistance of BaCeO₃on the premise of ensuring conductivity;On the other hand,the method of ion co-doping is used to control the crystal structure of BaCeO₃,then study its conductivity and corrosion resistance.In this paper,BaCeO₃-based electrolytes were synthesized by solid-state method and sol-gel method,respectively.The effects of electrolytes structure on electrochemical performance and corrosion resistance were studied.The main research results are as follows:（1）BaCe_1-xM_xO₃（x=0.15,0.2;M=Y,Gd）were prepared by the high-temperature solid-state method,the results show that the best sintering temperature is 1650°C and BaCe_0.85Y_0.15O_3-δ-Y₂O₃has the best electrochemical performance.The addition of Y₂O₃does not change the structure of BaCe_0.85Y_0.15O_3-δ,The density and conductivity decreased slightly,but the corrosion resistance in water vapor and CO₂can be improved.The electrical conductivity of BaCe_0.85Y_0.15O_3-δ-0.075Y₂O₃is 1.02×10^-2S·cm^-1and 1.43×10^-2S·cm^-1in air and 5%H₂/Ar+4%H₂O atmosphere at 600°C,respectively.After 8 h corrosion in CO₂and water vapor atmosphere at 600°C,the electrical conductivity of BaCe_0.85Y_0.15O_3-δ-0.075Y₂O₃is 0.71×10^-2S·cm^-1and1.16×10^-2S·cm^-1,respectively.The electrical conductivity is higher than that of BaCe_0.85Y_0.15O_3-δ,so the addition of Y₂O₃improves the corrosion resistance and electrical conductivity of BaCe_0.85Y_0.15O_3-δafter corrosion.（2）The best conditions of sol-gel method to synthesize BaCe_0.85Y_0.15O_3-δelectrolyte were studied.It is determined that the ratio of PVA,glycerol and matrix is 0.3:0.3:1,calcination temperature is 900°C,calcination time is 10 h,the crystal structure of the prepared BaCe_0.85Y_0.15O_3-δis a perfect orthogonal perovskite structure.The addition of ZnO improves the density and electrochemical performance of BaCe_0.85Y_0.15O_3-δ.When the mass of ZnO is 2%and the sintered condition is 1500°C 10 h,the density reaches 93.5%.The electrical conductivity of BaCe_0.85Y_0.15O_3-δare 0.75×10^-2S·cm^-1and 1.05×10^-2S·cm^-1at 600°C in air and 5%H₂/Ar+4%H₂O,respectively.Under the same synthesized conditions,the conductivity of BaCe_0.85Y_0.15O_3-δ-0.075Y₂O₃are0.57×10^-2S·cm^-1and 0.86×10^-2S·cm^-1at 600°C in air and 5%H₂/Ar+4%H₂O,respectively.（3）BaCe_1-xY_0.15Ni_xO_3-δ（x=0.02,0.04,0.06）and BaCe_0.8Y_0.1Ni_0.04Sm_0.06O_3-δwere prepared by sol-gel method.Ni doping can effectively improve the density of BaCeO₃sintered materials.When Ni doping amount is 0.04,the BaCe_0.85Y_0.15O_3-δhas a relative density of 92.5%.Sm doping can further improve the sintering density to94.1%.The electrical conductivity is 1.59×10^-2S·cm^-1and 2.23×10^-2S·cm^-1in air atmosphere and 5%H₂/Ar+4%H₂O atmosphere at 500°C.Compared with BaCe_0.81Y_0.15Ni_0.04O_3-δ,BaCe_0.8Y_0.1Ni_0.04Sm_0.06O_3-δhas excellent chemical stability because the electronegativity of Sm is greater than that of Ce.After corrosion treatment,the main BaCeO₃phase structure of BaCe_0.8Y_0.1Ni_0.04Sm_0.06O_3-δremains more complete.After 8 h corrosion in CO₂and water vapor atmosphere at 600°C,the electrical conductivity is 0.72×10^-2S·cm^-1in air atmosphere and 1.01×10^-2S·cm^-1in5%H₂/Ar+4%H₂O atmosphere.