Research On The Performance Of Cation Modified Strontium Ferrite Perovskite As SOFC Electrode Material

Solid oxide fuel cell（SOFC）is a new power generation technology with high efficiency and environmental protection,which can efficiently convert chemical energy into electrical energy.Therefore,it has attracted wide attention from researchers at home and abroad.In this paper,SrFe O_3-δ,a SrFe O_3-δ-based perovskite cathode material with good catalytic activity,was used as the research object.In view of the poor stability,high thermal expansion coefficient（TEC）and poor battery performance when it was used as the cathode of SOFC,Cu,Cu and Ti,and Cu and Nb were used to partially replace the B-site Fe element to modify its structure,respectively.The cubic phase structure of the material was stabilized,the cathode stability was improved,the TEC was reduced,the catalytic activity of oxygen reduction reaction（ORR）was improved,and the electrochemical performance of SrFe O_3-δas the cathode material of single cell was improved.A certain amount of copper-doped single-titanite cathode material SrFe_1-xCu_xO_3-δ（x=0.1–0.4）was synthesized by solid-state method.SFCx).XRD results showed that the sample sintered at 1000 ^℃ for 10 h had a cubic perovskite structure.Copper doping increases the oxygen vacancy concentration.With the increase of copper doping amount,the conductivity of SFCx increases first and then decreases.For example,at 700 ^℃,the interface impedance（ASR）decreased from 0.236Ωcm²（x=0）to 0.156Ωcm²（x=0.2）;when the cathode material with x=0.2 was used as the cathode to assemble the single battery,the maximum power density（MPD）in the series reached 625 m W cm^-2（800^℃）.Based on the excellent electrochemical properties of SFCx,B-site Cu and Ti co-doped SrFe_0.7Cu_0.2Ti_0.1O_3-δ（SFCT）single perovskite cathode materials were prepared by solid state reaction method.SEM results show that Ti doping improves the sintering properties and reduces the thermal expansion coefficient of the material.The TEC of the sample is only 13.8×10^-6K^-1.The introduction of Ti⁴⁺effectively improved the redox stability of the material.At 800 ^℃,the ASR and MPD of the cathode were 0.037Ωcm²and 785 m W cm^-2,respectively.The SFCT-xGDC（x=10,20,30,40）composite cathode material was prepared and its electrochemical performance was further optimized.The results show that the composite cathode material with the best composite ratio of SFCT-20GDC has the lowest impedance and the best single cell performance at 800 ^℃,which are 0.032Ωcm²and 756m W cm^-2,respectively.The Cu and Nb co-doped SrFe_0.7Cu_0.2Nb_0.1O_3-δ（SFCN）cathode material was further prepared by the solid-state reaction method.The maximum conductivity of the sample is123 S cm^-1（550 ^℃）,which is higher than that of SFCT.The co-doping of Cu and Nb effectively improved the electrochemical performance of the material and further improved the stability of the material.At 800 ^℃,the ASR of the SFCN cathode was 0.029Ωcm².The cathode impedance under different oxygen partial pressure was tested.The results show that the catalytic activity of the cathode increases with the increase of oxygen content.The co-doping of Cu and Nb greatly improves the performance of single cell as cathode.The MPD of single cell reaches 958 m W cm^-2at 800 ^℃,which is much higher than most traditional cathode materials.The SFCN-xGDC（x=10,20,30,40）composite cathode materials were also prepared.The MPD of SFCN-30GDC with the optimal composite ratio was increased to 1021 m W cm^-2at 800^℃.