Research On Structure Control Of Ni-Fe Anode In Solid Oxide Fuel Cell

Solid oxide fuel cell（SOFC）has attracted more and more attention because of its wide application,high efficiency and high utilization value of waste heat.Ni-Fe porous alloy has the advantages of high conductivity,high mechanical strength and so on.It is a promising anode material for SOFC.In order to improve the power density of SOFC,the structure and morphology of SOFC were investigated by means of XRD,SEM and porosity test.The anode material was prepared by chemical coprecipitation.The effects of Ni-Fe content and preparation process on the anode structure were studied.Because the working temperature of SOFC is too high,the electrochemical reaction process in the anode is difficult to observe in the working state.In this paper,Ni-Fe porous alloy anode supporting SOFC mathematical model is established.Electrochemical kinetics equation and mass,energy,momentum and charge conservation equation are used to describe the physical processes such as the flow,heat transfer and chemical composition transfer in SOFC.Coupling the transfer of concentrated matter,two times of current,chemical reaction,free porous medium flow and heat transfer in porous medium,the verified model was used to study the effect of anode internal chemical reaction process and anode structure parameters on the output performance of the SOFC,which provides a theoretical reference for the design of the anode structure of fuel cell.The best ratio of Ni-Fe support layer is Ni O+10 wt.%Fe₂O₃,the best sintering and reduction temperature are 1450^o C and 650^o C,respectively.When the sintering temperature exceed 1500^o C,the sample will deforme and have obvious crack.When the reduction temperature exceeds 750^o C,the sample cracks.The simulation results show that when the SOFC single cell is used as model,the temperature rises gradually from the inlet side along the flow direction,the temperature of the middle and rear reaches the highest and the outlet side temperature is slightly lower,the methane reforming reaction in the SOFC anode occurs mainly in the region near the gas channel at the bottom of the anode,which provides H₂ for electrochemical reaction and also consumes the H₂O and heat produced by the electrochemical reaction.The concentration of CH₄,CO and H₂ in the fuel gas decreases along the flow direction,and the concentration distribution of CO₂ and H₂O is opposite to CO and H₂.In the thickness direction of SOFC,concentration decreases slightly due to the mass transfer resistance of the porous medium.Comparing the three kinds of fuel gases,it is found that reducing the porosity of the anode function layer,increasing the porosity of the anode support layer and reducing the thickness of the anode support layer can improve the power density of SOFC,and the anode concentration polarization can be reduced by optimizing the structural parameters of the anode support layer.