Preparation And Performance Of Pr_0.4Sr_0.6Co_0.2Fe_0.7Mo_0.1O_3-δ Exsolved Anode Materials For Solid Oxide Fuel Cells

Under the dual pressure of energy crisis and environmental pollution,Solid oxide fuel cells（SOFCs）are able to convert various fuels（including hydrogen,hydro-carbon fuels,syngas）into electricity with high efficiency and low emission without combustion,which have also the advantages of using noble metal-free catalysts,all solid-state system and promising fuel flexibility,which have attracted increasing attention.SOFCs anode is an important catalytic reaction site,so the anode catalysts appear to be particularly important.Currently,the commercial anode is mainly Ni-based anode.The main limitations of SOFCs for long-term operational stability are the problems faced by the conventional the most widely used nickel-based cermet anodes such as redox-cycling instability,tendency towards agglomeration of Ni particles at high temperature and low coking resistance as well as sulfur resistance.The perovskite,redox-stable oxide anode materials,have been reported to be able to convert to composite anode materials by exsolving endogenous metallic nanoparticles socketed into the parent oxide substrates through in situ reduction,therefore exhibit highly enhanced electric conductivity and catalytic performance.Furthermore,the strong interaction between the metallic nanoparticles and the oxide substrate further suppresses the agglomeration,and allow the materials to be regenerative through redox-cycling,which are therefore proved to be promising SOFC anode materials.Firstly,in this work,the PSC_xF_0.9-xM perovskite precursor materials were designed and prepared,and the parent phase perovskite PSC_0.2FM with Co doping ratio of 0.2 was obtained with the best performance.A redox reversible composite anode reduced-Pr_0.4Sr_0.6Co_0.2Fe_0.7Mo O_3-δ(R-PSC_0.2FM)with Co-Fe alloy nanoparticles in situ growth on Ruddlesden-Popper phase-like perovskite oxides substrates has been prepared by reducing perovskite oxide material Pr_0.4Sr_0.6Co_0.2Fe_0.7Mo O_3-δat high temperature（900℃）.R-PSC_0.2FM composite anode has shown promising electrocatalytic performance to fuel oxidation,proton-conductor Ba Zr_0.2Ce_0.7Y_0.1O_3-δ（300μm）electrolyte supported single cells based on R-PSC_0.2FM anodes achieves a maximum power density of 172.6 m W?cm^-2 in humid H₂（3vol% for Solid Oxide Fuel Cells H₂O）.According to the polarization impedance spectrum of the symmetrical half-cell,the polarization impedance of the anode is mainly contributed by the middle frequency,which indicates that the gas diffusion process is not very smooth inside the electrode.It is possible that the electrode may not be very uniform,and the process needs to be improved.According to the trend of SOFCs development,efficient use of hydrocarbon fuel has become a very important research direction.When using hydrocarbon fuels,the common problem of SOFCs is carbon deposition.We improve the performance of porous anode by doping CeO₂.The maximum power densities of CeO₂-R-PSC_0.2FM using wet hydrogen as fuel is 253.2 m W?cm^-2 and dry ethane as fuel is 182.9 m W?cm^-2 at 750℃.Moreover,in the constant pressure stability test（10 h）of ethane fuel gas,the single cell without doping CeO₂ is relatively stable,and no obvious attenuation,while the current of single cell with doping CeO₂ is increasing.And the carbon tube with carbon deposition appeared in the cell anode porous structure without doping CeO₂ after the stability test,which shows that the doping CeO₂ has a significant effect on carbon deposition resistance.When ethane is used as fuel,the exhaust gas of single cell is analyzed under the condition of maximum discharge power.Ethylene is a very important chemical in petrochemical industry.The single cell with a structure of CeO₂-R-PSC_0.2FM-BZCY/BZCY/LSCF-SDC at a working temperature of 750℃ has a ethane conversion of 36.04%,ethylene selectivity of 94.61%and yield of 34.09%.