Performance Research Of Direct Ethanol High Temperature Fuel Cell Based On NiFe₂O₄ Inner Reforming Functional Layer

The most attractive feature of the solid oxide fuel cell is that it can use a range of combustible fuels,including hydrogen,carbon monoxide,hydrocarbons,synthesis gas,and oxygen-containing hydrocarbons.Compared with other fuels,ethanol has many attractive physical and chemical properties and characteristics,including its high energy density,easy transportation and storage.In addition,ethanol can be produced in large quantities at low prices,and ethanol is a renewable fuel,which is very suitable for SOFC fuel.The development of efficient and reliable conversion devices such as fuel cells with bio-alcohol as the main raw material can increase market penetration.Commercial traditional Ni-YSZ anode-supported single cells are prone to anode carbon deposits when ethanol is used as fuel,which further leads to degradation of the cell performance.Therefore,in order to solve the problem of carbon deposition on the anode of ethanol SOFC,this paper mainly studies the problem of anti-carbon deposition of the traditional Ni-YSZ anode from the perspective of fuel and anode reforming layer materials.Firstly,a simple low fuel partial pressure method was used to study the limiting factors of ethanol SOFC.As the partial pressure of ethanol fuel increases from 30%to60%,the best cell performance gradually increases from 710.2 m W cm^-2to 856.8 m W cm^-2at 800℃,which still lower than those of hydrogen-fueled SOFCs(1061.4 m W cm^-2at 800℃),and the corresponding improvement in concentration polarization can be clearly observed especially in high current discharge area.The corresponding impedance spectra and electrode polarization processes of ethanol-fueled SOFCs are further studied by the equivalent circuit fitting and the distribution function of relaxation time（DRT）analysis,finding that the key improvement of the speed control steps comes from the concentration polarization process with the increase of the fuel partial pressure.Small amount of carbon deposition is observed on the Ni-YSZ anode substrate by SEM-EDS images after short-term discharging testing,and the safety utilization boundaries of ethanol-fueled SOFCs with a certain steam concentration can be predicted by the thermodynamic equilibria calculation.Secondly,in order to further solve the problem of carbon deposition on the ethanol SOFC anode,a reforming layer was added on the surface of the cell anode,and Ni Fe₂O₄and Ni Fe₂O₄-GDC were selected as the reforming layer materials.When the test temperature is 800℃,the maximum power density of the sintered1200℃Ni Fe₂O₄reforming layer cell is 1027.1 m W cm^-2,the impedance is 0.50Ω,the electrochemical stability is good,and the anode carbon content is relatively small.The maximum power density of the sintered 1100℃Ni Fe₂O₄-GDC reforming layer cell is1069.7 m W cm^-2,the impedance is 0.36Ω,the electrochemical stability is good,and the anode carbon content is relatively small.Finally,the solution of steam reforming ethanol fuel is used to further study the problem of SOFC anode carbon deposition.Under the same test conditions,the electrochemical performance of the two reforming layer cells is higher than that of the non-reforming layer cell,and the power reduction and polarization resistance of the Ni Fe₂O₄-GDC reforming layer cell are smaller than those of the Ni Fe₂O₄reforming layer cell.Steam reforming of ethanol can reduce the carbon deposition on the anode of the cell to a certain extent,but no matter which kind of cell is tested,there is carbon in the anode,but the shape of carbon has obvious difference.There are 43 figures,2 tables and 87 references in this article.