Preparation,Optimization And Electrochemical Performance Study Of Ni-Subsituted Sr(Ti,Fe)O₃-Based Composite Anode

Solid oxide fuel cells(SOFCs)are an attractive electrochemical energy conversion technology with high efficiency and environmentally friendly properties,which has attracted increased interest.The development of SOFCs in recent decades suggests that it has great potential in alleviating future energy crises.Currently,the development of SOFC operated at medium temperature(600-800^oC)is highly desirable.However,reducing the operating temperature will suppress the electrochemical hydrogen oxidation reaction activity,thereby resulting in increased anode polarization loss and reduced performance.Nowadays,the practical application is restricted by the insufficient anode catalytic activity and working life of SOFCs.In this paper,based on the Sr(Ti,Fe)O₃-based mono-perovskite oxide Sr Ti_0.3Fe_0.7O_3-?(STF),we investigated the B site is doped with Ni,the A vacancy is introduced and the ratio of Ti is increased,as well as the effects of the evolution of structure and electrochemical performance.Meanwhile,the resultant composite anode after incorporating the second phase of Gd_0.1Ce_0.9O_2-?(GDC)cation conductor was employed to evaluate its performance under syngas.Performing equivalent circuit fitting analysis on the measured electrochemical impedance spectra can further understand the intermediate process of the electrode reaction and determine the rate-determining step(RDS)of the intermediate reaction,hence providing references and ideas for optimizing the anode reaction.First,we propose an optimized perovskite Sr_0.95Ti_0.35Fe_0.6Ni_0.05O_3-?(STFN)anode composition and optimize the working conditions.At about 600^oC,the conductivity of STFN reaches 13-15S/cm.At 750°C,0.8 V voltage,and different hydrogen partial pressures(₂),STFN single cells show excellent output power.The cell voltage of constant current discharge is maintained at 0.745 V for 110 hours without obvious degradation,suggesting robust long-term stability.In addition,the anode reaction process has been further improved after adding GDC,the composite anode mixed ion electronic conductivity has been greatly improved,so the anode oxidation capacity is improved.Under the condition of 750^oC,the_,of the anode of STFN-GDC is smaller than that of STF-GDC,and the slope values of_,and₂of STF-GDC and STFN-GDC are 0.351 and 0.282,while STF and STFN are 0.284 and 0.292,respectively.It promotes the practical application of perovskite anodes.Finally,the STFN and Gd_0.1Ce_0.9O_1.95(GDC)composite(STFN@GDC)electrode was prepared by a sol-gel method,which was employed as the anode functional layer of the electrolyte-supported single cell.Experimental studies revealed that the STFN@GDC composite anode can reduce the dependence of anode polarization resistance in low-concentration fuels and increase the ohmic resistance,thereby improving anode performance.Under the condition of 750^oC and₂=0.97(68),the STFN@GDC anode_,decreased by 0.089?·cm².Besides,STFN@GDC single cell also showed good performance under the atmosphere of H₂ and H₂-CO.