Study On Performance Of Fibrous La_0.8Sr_0.2FeO_3-δ-based SOFCs Cathode Materials

Solid oxide fuel cells（SOFCs）are one kind of electrochemical devices that convert the chemical energy into electricity directly,having the advantages of high energy conversion rate and low environmental impact.At present,in order to reduce the cost of cell materials and extend the working life of equipment,operating at intermediate and low temperatures is its main development trend.Cathode is one of the important parts to determine the overall cell performance.However,lowering the operating temperature will result in an increase in cathode polarization loss and reduced oxygen reduction reaction（ORR）catalytic activity.The relatively slow cathode kinetics limits the improvement of electrochemical performance.La_0.8Sr_0.2Fe O_3-δ（LSF）has attracted much attention for SOFCs cathode materials due to its high electronic and ionic conductivity,good long-term stability.Nevertheless,its catalytic activity is still lower than that of common cobalt-based perovskite oxide cathodes.In order to further improve the catalytic activity of LSF cathode,this paper takes LSF nanofibers cathode as the research object,improving its electrochemical performance through element doping and surface modification.The main research contents and results are as follows:（1）LSF nanofibers were prepared by electrospinning method,the“A”site was doped with Bi elements.A series of La_0.8-xBi_xSr_0.2Fe O_3-δ（LBSFx,x=0.0～0.5）cathode materials with fibrous structure were obtained,and their electrochemical behavior was tested.The results show that the La_0.4Bi_0.4Sr_0.2Fe O_3-δ（LBSF4）cathode has the lowest polarization resistance,and the polarization resistance value of LBSF4 cathode measured at 650°C is 0.126Ω·cm².The LBSF4 nanofiber cathode is applied to the Ni-SDC anode-supported SDC electrolyte single cell.The maximum power density of the single cell measured at 650°C is 448 m W·cm^-2.（2）LSF nanofibers were prepared by electrospinning method,the“B”site was doped with Cu elements.A series of La_0.8Sr_0.2Fe_1-xCu_xO_3-δ（LSFCux,x=0.0～0.3）cathode materials with fibrous structure were obtained,and their electrochemical behavior was tested.The results show that the La_0.8Sr_0.2Fe_0.8Cu_0.2O_3-δ（LSFCu2）nanofiber cathode has the best electrochemical performance.The polarization resistance value of LSFCu2 cathode measured at 650°C is 0.674Ω·cm²,the maximum power density of Ni-SDC/SDC/LSFCu2 single cell is 362 m W·cm^-2.（3）On the basis of LSFCu2 nanofiber cathode,a series of LSFCu2-x Ba CO₃composite cathodes were prepared by chemical impregnation method,and the influence of Ba CO₃ impregnation amount on electrochemical performance was studied.The results show that LSFCu2-20.57 wt%Ba CO₃composite cathode has the best electrochemical performance.The polarization resistance of composite cathode measured at 650°C is 0.121Ω·cm²,compared with the cathode without Ba CO₃nanoparticles,the polarization resistance is reduced by about 5 times,and the electrochemical performance significantly improved.The maximum power density of Ni-SDC/SDC/LSFCu2-20.57 wt%Ba CO₃ single cell is 498 m W·cm^-2 measured at650°C.