Influence Of Cu Addition For The Mechanical And Electrochemical Properties Of SOFCs Anode Materials(Ni-YSZ)

The solid oxide fuel cell?SOFC?as a high-efficiency electrochemical device that can directly convert the chemical energy of the fuel into electrical energy currently has several major problems to be solved:?1?reducing the preparation and operating temperature;?2?solve the problem of anode carbon deposition when the cells operates in carbon-based fuel as the reaction gas;?3?develop new electrode materials with more excellent performance to meet the more stringent operating conditions of the cells.In this thesis,we will systematically study the low-temperature sintering technology of SOFC,the corresponding anti-carbon deposition capacity of the anode and the development of a new anode material for the above problems.In one part,firstly,we demonstrate that the appropriate amount of CuO as sintering aids included in anode can successfully reduce the co-firing temperature of conventional micron size NiO-YSZ(yttrium-stabilized zirconia?Y₂O₃?_0.08?ZrO₂?_0.92)anode from about 1400 ^oC to only 1100 ^oC.Second,the quantitative structure-activity relationship among the mechanical strength?low-temperature sintering ability?of anode materials with the inclusion of CuO contents and the densification of YSZ electrolyte was synthetically evaluated.The optimal CuO-NiO-YSZ anode composition?sintering at 1100 ^oC?demonstrates almost the equal mechanical strength when compared with the traditional NiO-YSZ anode?sintering at 1400 ^oC?.And the maximum power density of single cells prepared by adding appropriate amount of CuO at 800?using hydrogen and methane gas as fuel gas can reach 524 mW cm^-2 and 345 mW cm^-2,respectively.During the long-term stability test of the single cells,using dry methane gas as fuel gas,the cells have excellent stability.At last,by comprehensive assessment,8%CuO-52NiO-40YSZ?8%CuO-NiO-YSZ?shows excellent low-temperature sintering ability,high mechanical strength,optimal power output,and anti-carbon deposition when using as hydrocarbon-based anode for SOFCs.In another part,a high-efficiency IT-SOFCs catalyst with H⁺/O^2-/e^-triple-conduction mechanism was developed.We modified La₂Ce₂O₇ to improve its intrinsic proton conductivity,and introduced efficient electron and oxygen ion conduction to build H⁺/O^2-/e^-triple-conduction mechanism which used as the anode layer of SOFCs to achieve the purpose of improving performance of SOFCs.Firstly,the crystal structure type and internal ion valence of La₂CePrO₇were proved.The crystal structure of samples is cubic fluorite structure,and the space group is Fm3?8)Secondly,We also evaluated the H⁺/O^2-/e^-triple-conduction mechanism of La₂CePrO₇material.On the one hand,the total conductivity of La₂CePrO₇ was measured by DC four-terminal method at different temperatures in air and H₂ atmosphere respectively.Based on the gas separation technology,La₂CePrO₇ dense ceramic pieces were prepared.The oxygen and hydrogen permeability were tested under high purity O₂ and H₂,respectively.Based on electrochemical impedance spectroscopy technology,symmetric half-cells were assembled on La₂CePrO₇ ceramic pieces,and the resistance of samples changed under different water vapor partial pressures were tested to demonstrate the proton conduction.On the another hand,assuming that La₂CePrO₇ is a pure ionic conductor,we calculated the open circuit voltage of N₂/Ag|La₂CePrO₇|Ag/air cell model as a function of temperature theoretically.After assembling the above cell model and testing its actual open circuit voltage at different temperatures,we compared with the theoretical OCV value.By comparison,the ratio of electron to ion conductivity is obtained.And then,add the total conductivity measured by the four-terminal method to calculate the electronic conductivity of La₂CePrO₇ at different temperatures.Moreover,the oxygen ion/proton(O^2-/H⁺)conductivity was evaluated.Finally,the catalytic performance of samples were evaluated,and the samples were successfully applied to solid oxide fuel cells.The maximum power density of single cells at 800?reached 686 mW cm^-2using hydrogen as fuel.