The Preparation And Performance Of Molybdenum Disulfide As Anode Of Solid Oxide Fuel Cells

Solid oxide fuel cell（SOFC）is a new energy conversion technology with high efficiency and environmental protection.The direct use of hydrocarbon fuels is one of its development trends,but the traditional anode material Ni-YSZ（yttria-stabilized zirconia）will be poisoned which causes the performance degradation of cells in sulfur-containing atmosphere.The purpose of this work is to reduce or inhibit the sulfur poisoning of the anode,improving the comprehensive performance of the anode in hydrocarbon fuels,so that SOFC can be directly use hydrocarbon fuels,so as to reduce the operating cost of SOFC and promote its commercialization process.The results show that the use of sulfides as SOFC anode materials can effectively inhibit the sulfur poisoning phenomenon of the anode.In this work,by investigating the physicochemical properties of MoS₂ in different atmospheres at high temperature,and compounding with Ag of different volume fractions as SOFC anode materials,the electrochemical performance of single cells in H₂,250 ppm H₂S was tested.The following conclusions are obtained:（1）Characterization of MoS₂.MoS₂ powder can be oxidized to MoO₂ at high temperature in the atmosphere of nitrogen、high purity argon and 100 ppm H₂-N₂,and the rate of oxidation can be accelerated by increasing calcination temperature;MoS₂can be reduced to Mo in 500000 ppm H₂-N₂、H₂,and the amount of Mo can be reduced to increase calcination time;MoS₂ can be stable in 250 ppm H₂S-H₂.The conductivity of the MoS₂ sample strips was tested in different hydrogen partial pressures while ensuring its stable existence.The results show that the conductivity of MoS₂ increases with the increase of temperature.With the increase of hydrogen partial pressure,the conductivity also increases slightly,indicating that the measured conductance of MoS₂is electronic conductance,but there may be proton conductance.（2）Study on sulfur-tolerant anode materials for YSZ electrolyte-supported cells.The electrolyte sheets were prepared by dry pressing and sintering method,(La_0.8Sr_0.2)_0.98MnO₃（LSM）-YSZ as cathode,MoS₂、0.1Ag-MoS₂ and 0.2Ag-MoS₂ as anode,respectively,were prepared by screen printing and sintering for electrochemical performance test.The results show that the polarization of the electrodes decreases with the increase of temperature,under the same current density,the polarization overpotential of the anode decreases after the addition of Ag,it is still much larger than the overpotential of the cathode,which is one of the main factors affecting the electrochemical performance of the single cell.In 250 ppm H₂S-H₂ at 750℃,the single cell 0.2Ag-MoS₂/YSZ/LSM-YSZ has a maximum power density of 10.60 mW cm^-2and an ohmic impedance of 3.1Ωcm².In 250 ppmH₂S-H₂ at 700℃,constant current discharge was carried out for 180 min without obvious attenuation of performance.（3）Study on sulfur-tolerant anode materials for scandia stabilized zirconia（SSZ）electrolyte-supported cells.The electrochemical performance of the single cell prepared by the above three anodes was tested by changing the electrolyte material to SSZ and LSM-SSZ as cathode.The maximum power density of 0.2Ag-MoS₂/SSZ/LSM-SSZ was 39.56 mW cm^-2 and the ohmic impedance was 1.1Ωcm² in the atmosphere of 750℃and 250 ppm H₂S-H₂,but the excessive polarization overpotential of the anode is still one of the important factors that restrict the electrochemical performance improvement of the single cell.Through the research in this work,the feasibility of MoS₂ as SOFC sulfur-tolerant anode is confirmed,but the anode needs to be optimized further to improve the overall performance of the cell while ensuring the sulfur-tolerant property of the anode.