The Perparation And Performance Of The Perovskite Cathode For Low/Intermediate Temperature SOFC

Solid oxide fuel cell(SOFC)has been recognized by people for its advantages of high safety,high energy conversion and no pollution.The traditional SOFCs operate at high temperatures(?1000?)which can cause complex materials problems,such as electrode sintering and interfacial reaction between electrolyte and electrode materials,this will undoubtedly increase the cost of SOFC.It is imperative to develop intermediate temperature solid oxide fuel cells(IT-SOFC)cathode materials with high catalytic activity.This paper will focus on the catalytic activity of improving the cathode materials of IT-SOFC.The research includes the modified structure,the oxygen reduction mechanism,the long-term stability,the resistance to moisture and the ability to resist CO2.According to the research direction,the article can be divided into the following three parts:1.The effect of A-site cation deficiency on the electrochemical performance of the cathode material was investigated.The XRD analysis of powder S0.95CNF shows that Sr2+ has little effect on the crystal lattice of the cathode,while S0.95CNF cathode and SDC electrolysis have high chemical compatibility.It was found by iodometric titration test that the oxygen vacancy concentration of S0.95CNF increased than the SCNF.Under the condition of 700?,the polarization impedance of SCNF is 0.18 Qcm2,while the polarization resistance of S0.95CNF is 0.11 ?cm2,which is reduced by 38.9%.The electrolyte supported single cell by S0.95CNF as cathode had maximum power density of 208 mWcm-2,which was about 15.6%higher than SCNF cathode material.Therefore,the Sr0.95Co0.7Nb0.1Fe0.2O3-? is a very promising IT-SOFC cathode material.2.The electrochemical performance of cathode was improved by B sites doping.The Ni is used to replace the Co in the Sr0.95Co0.9-xNb0.1NixO3-? cathode.The thermogravimetry and iodometric titration tests show that the cathode material has a higher oxygen vacancy concentration with increasing Ni content,and get the maximum at x = 0.2.Meanwhile,the test of conductivity showed that the ionic conductivity of the material increases with the increasing Ni content.Under the condition of 700?,SCNN2 exhibited the best electrochemical performance with the polarization impedance and maximum power density of 0.066 ?cm2 and 396 mWcm-2.And it shows a high stability during the 160h long term testing and excellent water vapor tolerant of SCN-N2.3.This part mainly study the electrochemical performance of the composite cathode.The electrochemical catalytic performance of the composite cathode was improved by compounding SrCo0.7Nb0.1Ni0.2O3-? with SDC.The ECR test results show that the oxygen diffusion coefficient and exchange coefficient of the cathode material after SCNN composite SDC increase.We concluded that composite SDC effectively enhance the composite cathode electrocatalytic performance.Under the condition of 700?,the polarization impedance and maximum power density are 0.019 ?cm2 and 623 mWcm-2 of SCNN-40SDC.And SCNN-40SDC has a high stability during 140h long term testing and while still maintain high performance under the CO2 atmosphere.