Study On Modification Of Anode And Electrolyte In Liquid Antimony Anode Solid Oxide Fuel Cell

Solid oxide fuel cell（SOFC）is a safe,efficient and environmentally friendly electrochemical energy conversion device.Traditional anode-supported SOFCs mostly use gaseous fuels for power generation,and the ustilization of solid fuels is severely limited by the porous anodes.The liquid metal anode SOFC adopts liquid metal or alloy as the anode,which has a very good resistance to fuel ashes and impurities,and the liquid state of anode improves its contact with the solid fuel,so it has the ability to efficiently convert solid fuelto electricity.Sb metal has been proven to be a suitable liquid metal anode for DCSOFC due to its appropriate melting point.Current researches find that the corrosion of common electrolytes by liquid Sb anodes has greatly limited its life and application.The open circuit potential（OCV）of the liquid Sb anode SOFC is also lower than that of the cells using a gaseous fuel.,which meansa lower theoretical electrical energy conversion efficiency,and a serious energy decline.To address the above issues,this article firstly explored the feasibility of using Fe-Sb alloys as liquid anodes at 800°C;secondly,the long-term stability and corrosion resistance of GDCF（GDC with a small amount of Fe₂O₃）and YSZM（YSZ with a small amount of Mn O）were investigated and the mechanism of the improved corrosion resistance was illuminated.The main works and results are as follows:（1）Firstly,a half-cell with YSZ electrolyte was prepared by the tape casting method,and the electrochemical performance at initial stage of the Fe-Sb alloy anodes with different proportions of Fe elements（0wt.%,5wt.%,10wt.%）was tested at 800°C.SEM and EDX element analysis were performed on the surface and of crossscetion of electrolytes after the test.The results showed that the addition of a small amount of Fe（5wt.%）to the Sb anode didn’t affect the OCV of the cell after a short time discharge,but accelerated the anode material transport process;On the other hand,adding too much Fe element（>10wt.%）to Sb anode would generate the Fe₂O₃ during the short-term discharge process and greatly affect the O^2-transport process,and then lead the electrochemical performance of the cell drop sharply.（2）Firstly,GDCF electrolytes mixed with different proportions of Fe₂O₃（1mol.%,2mol.%and 3mol.%）were prepared by die-pressing method.Then the corrosion phenomena of GDCF electrolytes under liquid Sb and Sb₂O₃ environment and electrochemical corrosion behavior under Sb environment at 750oC were observed.The results indicated that GDCF-2（GDC mixed with 2mol.%Fe₂O₃）showed the best corrosion resistance:In liquid Sb and Sb₂O₃,the thickness of the corrosion layer were 60μm and 4μm,respectively.The thickness of the corrosion layer after the electrochemical test was only 2/5 of the GDC electrolyte under the same conditions.Combining SEM morphology and EPMA elemental analysis,GDCF-2electrolyte had small grains size and longer grain boundaries in per unit volume,which meant the route of Sb penetration through the grain boundaries became more tortuous,and it’s more difficult to penetrate deep into the electrolyte.By fitting and analyzing the electrochemical impedance spectraduring electrochemical corrosion,it was found that the change in ohmic resistance can be an effectively monitor for the electrolyte corrosion depth.（3）In termsof the different corrosion mechanisms of YSZ and GDC electrolytes,a different schemes was adopted for the YSZ electrolyte to enhance its resistance to corrosion.YSZM（YSZ electrolyte with 2mol.%Mn O）electolytes were prepared and tested for stability in the liquid Sb and Sb₂O₃ environment.The cross-sectional morphology of the sample after the test was subjected to SEM and EDX elemental analysis.With a small amount of Mn O,YSZ had larger crystal grains,which effectively decreased the grain boundary weak areas on the surface of the electrolyte and let thedissolving of grain boundaries by Sb₂O₃ become more difficult.The results showed the addition of Mn element significantly improved the corrosion resistance of YSZ electrolyte.