Study On Cathode Optimization And Performance Of Intermediate-Temperature Solid Oxide Fuel Cells

Solid oxide fuel cell(SOFC)is a very promising new energy technology,but the higher operating temperature for the SOFC(800-1000?)seriously restricts its commercial development.In order to promote the use of SOFC,it is imperative to reduce the operating temperature of the SOFC to the intermediate-temperature range(500-700?).But a significant effect of reducing the operating temperature of the SOFC is an increase in the loss of cathodic polarization,which is very significant.In this paper,the cathode of Oxygen-based Solid Oxide Fuel Cell(O-SOFC)was studied.And the cathodic microstructure was improved by ion impregnation method.By the way,the cathode performance at intermediate-temperature was proved too.The first chapter of the paper briefly describes the working principle of Solid Oxide Fuel Cell(SOFC)and the development status of material,which is used in the various parts of oxygen ion conductor based solid oxide fuel cell(O-SOFC).Also,the cathode reaction process and a Cathcde optimization method-ion dipping method are introduced in this chapter.In the second chapter,the ESB/La0.8Sr0.2MnO3-s(LSM)composite cathode compatible with En0.4B1.6O3-?(ESB)electrolyte was prepared by ion dipping method,and its electrochemical performance was tested.The performance of the ESB-LSM composite cathode is divided into two parts:one is to measure the impedance spectrum of the symmetrical battery;the other is using the ESB-LSM composite cathode onto the GDC/ESB bilayer electrolyte battery and testing its electrochemical performance.The results of the symmetric battery impedance spectra show that the performance of LSM-ESB composite cathode has a great relationship with the mass ratio of LSM and ESB.When the mass fraction of LSM is less than 30%,the polarization of LSM-ESB composite cathode is more serious and the cathode performance is poor.However,if the mass fraction of LSM is more than 60%,too much LSM will block the partial pores of the porous ESB skeleton,so that the TPB of the oxygen reduction reaction in the cathode decreases and the cathode performance decreases.Between these two cases,LSM-ESB composite cathode has low polarization resistance and good cathode performance when the mass fraction of LSM is between 40%and 50%.The performance of the obtained single cell is better than that of the conventional mechanical mixing method,especially in reducing the cathodic polarization resistance.The third chapter is the NiO-SDC anode powder incorporate BaO in the preparation process firstly.Then,During the sintering of the anode-supported half-cell,BaO volatilizes and contacts with SDC to produce BaCeO3.In this mixed ion conductor,BaCeO3 has a certain anti-carbon deposition capacity.On this basis,we prepare composite cathode by ion impregnation method to further enhance the performance of the battery.In the experiment,the ion-impregnated cathode is more superior to the cathode performance prepared by the mechanical blending process,especially the polarization resistance.At 650 ?,the polarization resistance of the composite SDC-SSC cathode prepared by ion dipping method is 0.058? cm2,which is about 60%smaller than that of the cathode prepared by ordinary mechanical mixing method(0.142? cm2).It is proved that the preparation of the composite cathode by ion impregnation can reduce the polarization resistance of the cathode.Moreover,the single cell with composite cathode prepared by ion dipping has an output power of 600 mW · cm-2 at 650 ?,which is higher than the output power of the battery prepared by the mechanical mixing method.The above results show that the composite cathode of SOFC prepared by ion impregnation method has better performance than the cathode prepared by traditional mechanical mixing method.Ion impregnation method is a valuable cathode optimization method.In the fourth chapter,the paper summarizes the work of the graduate students,and prospects the application prospect of the ion dipping method in the preparation of low temperature SOFC electrode materials.It is not sufficient to use the ion dipping method for cathodic modification only.The modification of the SOFC anode can also be carried out by ion impregnation.For example,in the third chapter of the work,we can also use NiO-SDC anode and SDC electrolyte powder by dry pressing and high temperature sintering.The anode side was impregnated with Ba(NO3)2 solution.It has been reported that BaO has excellent resistance to carbon deposition on Ni surface deposits.We can also make the BaO deposited on the Ni surface by ion impregnation,so that it can contact with Ni for a large area to improve its ability to resist carbon deposition.