Study On Modification And Electrochemical Properties Of Layered Perovskite PrBaCo₂O_5+? Cathode Material For Solid Oxide Fuel Cells

This work is based on intermediate temperature solid oxide fuel cell,choosing mixed conductor PrBa Co2O5+d as the cathode material.The main purpose is to improve the comprehensive properties of the cathode material.The PrBaCo2-xMnxO5+d(PBCM-x,x=0.1,0.2 and 0.3)cathode materials are studied systematically.PrBaCo1.9Ni0.1O5+d(PBCNO)–x Ce0.8Sm0.2O1.9(SDC)(x=0,10,20,30,40 and 50 wt%)composite cathodes are prepared,and the effects of SDC content on thermal expansion behavior,electrical conductivity and electrochemical performance of the PBCNO–xSDC composite cathodes are systematically investigated.The cathode materials PBCM-x and PBCNO were prepared by a combined EDTA-citrate complexing sol-gel method.XRD results show that after calcination at 1000 °C in air for 5 h the PBCM-x and PBCNO exhibite a tetragonal structure with the space group of P4/mmm.The substitution of Co by Mn lowers the thermal expansion coefficient clearly.The average TEC decreases from 22.8×10-6 K-1 for PBCM-1 to 15.1×10-6 K-1 for PBCM-3 in the temperature range of 35-800 °C.All the samples reach the generally required electrical conductivity value of cathode material at the operating temperature range of 600-800 °C.Electrochemical performances of PBCM-2 are better than those of other materials of the same series.The polarization resistance of PBCM-2 is 0.72,0.25 and 0.09 ? cm2 at 700,750 and 800 °C,respectively.The power density of the single fuel cell is 124.1,236.7 and 304.2 mW cm-2 at 700,750 and 800 °C,respectively.PBCNO–x SDC composite cathodes were prepared.XRD results show that PBCNO was chemically compatible with the SDC electrolyte.The thermal expansion coefficient and electrical conductivity decrease with the increase of SDC content.The addition of SDC reduces the polarization resistance.The lowest polarization resistance of 0.012 ? cm2 is achieved at 800 °C for the PBCNO–40SDC composite cathode.At the same time,the PBCNO–40SDC composite cathode delivers the highest power density of 483.1 mW cm-2 at 800 °C.