Preparation And Properties Of Double Perovskite Cathode Materials For SOFC

The PrBa_0.85Ca_0.15Co₂O_5+??PBCC?was chosen as the cathode material of skeleton,which were prepared respectively by sol-gel method?the coprecipitation method?the EDTA-glycine method and the glycine-nitrate method,Thermal analysis of the materials was carried out.The phase,the cross section of the bead and the microstructure and electrochemical properties of the powder were tested to explore the advantages of PBCC for the cathode skeleton of a medium temperature solid oxide fuel cell?SOFC?and the method used to obtain the effect.better.According to the analysis of thermogravimetry-differential heat?TG-DTA?,in order to ensure the preparation of stable double perovskite composite materials by four methods,the calcination temperature of colloid and precipitate was set at 1000?.The XRD test showed that after the prepared PBCC cathode material was processed,no impurity phase appeared,and a tetragonal type perovskite phase was formed.The microstructure of the scanning electron microscope?SEM?shows that the particle size of the material obtained by the sol-gel method is the smallest and the particle shape distribution is the most regular,and the sintering performance is good,which is beneficial to improve the chemical properties.The conductivity test knows:In the atmospheric environment,the conductivity of PBCC prepared by sol-gel method is higher than that of the other three methods in the temperature range of 400-800?,which is the highest at 800?,928 S/cm,and the lowest is400?.The 431 S/cm,coprecipitation method has a conductivity of at least 250 S/cm and meets the requirements of not less than 100 S/cm.The thermal expansion coefficient of the cathode material prepared by the coprecipitation method is at least 19.3×10^-6 K^-1,and the sol-gel method is lower than the other two methods.In view of the excellent electrochemical performance of the PBCC prepared by the sol-gel method,Higher TECs can be used to prepare the desired IT-SOFC cathode material by doping a transition metal element with SDC.In order to study the doping range of transition metal elements,the ratio was set to 1:1,and the PrBa_0.85Ca_0.15CoMO_5+??M=Fe,Mn,Ni,Cu?cathode materials were prepared by sol-gel method.Radiation diffraction?XRD?,scanning electron microscopy?SEM?,DC four-electrode method,and thermal expansion coefficient?TEC?test were tested.The results show that the PBCCM?M=Fe,Mn,Ni,Cu?prepared by sol-gel method is a double perovskite structure,the cathode powder particles are small and evenly distributed,and the temperature is gradually increased from 400?to 800?.In the middle,the conductivity of PBCCM has been decreasing,which is consistent with the metal-like conductive mechanism.The conductivity of doped Cu material is greater than that of Fe,Mn and Ni,reaching a maximum of 451S/cm at 400?.The incorporation of Mn,Ni and Cu can significantly reduce the thermal expansion coefficient of the PBCCM cathode material,and the effect is best.The Cu series cathode materials are doped in a larger range,with Pr?NO₃?₃·6H₂O,Ba?NO₃?₂,Ca?NO₃?₂·4H₂O,Co?NO₃?₂·6H₂O and Cu?NO₃?₂·4H₂O is used as raw material,EDTA-ammonia aqueous solution is a complexing agent,citric acid is used as an auxiliary complexing agent,and PrBa_0.85Ca_0.15Co_2-xCu_xO_5+??x=0.2,which can be used as a cathode material of SOFC?is prepared by sol-gel method.0.4,0.6,0.8,1;PBCCC),by thermogravimetry-differential thermal analysis?TG-DTA?,X-ray diffraction?XRD?,scanning electron microscopy?SEM?,DC four-electrode method,thermal expansion coefficient?TEC?,AC impedance Wait for the test.The research shows that the PBCCC cathode material prepared by sol-gel method forms a stable double perovskite structure after calcination at 1000?for a period of time.The doping of Cu promotes the particle size of the powder to be smaller,the particle shape is regular,the density is high,and sintering Good performance.In the atmospheric environment,the conductivity of PBCCC cathode material is up to 648 S/cm in the tempera ture range of 400-800?,and the minimum requirement is not less than 100 S/cm,and thermal expansion is achieved with high conductivity.The coefficient is obviously down-regulated.The TEC of PrBa_0.85Ca_0.15Co_2-xCu_xO_5+??x=1?is 16.21×10^-6K^-1,which is the best comprehensive performance.The conductivity of this series of cathode materials is the highest.The polarization resistance of PrBa_0.85Ca_0.15Co_2-xCu_xO_5+??0.4,0.6,1?is very small,which facilitates the transport of oxygen to the cathode material.The Fe,Mn,and Ni elements were doped in a small proportion,and the obtained cathode materials were subjected to the same characterization analysis.It was found that the addition of the three materials can reduce the TEC of the cathode material,but compared with the skeleton PrBa_0.85Ca_0.15Co₂O_5+?(The conductivity of PBCC is much lower,and the reduction of TEC is not very large.Combined with the previous study,the prepared PrBa_0.85Ca_0.15CoCuO_5+?is the best cathode material.