Study On Tubular Solid Oxide Cells Using Ammonia As Fuel

Energy is the foundation for human survival.In 2006,fossil fuels accounted for as much as 87.9% of the global energy consumption.It is expected that global energy demand will increase by 50% between 2020 and 2023.In the long run,fossil fuels will be consumed completely in this century.Therefore,developing efficient and clean fuel cells as a new generation technology to alleviate the contradiction between energy demand and environmental protection is of great significance.The performance of direct ammonia fuel SOFC is equivalent to that of hydrogen fuel SOFC,with good durability.However,when ammonia is directly utilized in fuel cells,nickel based cermet anodes react with ammonia,resulting in a decrease in activity.In order to alleviate the long-term stability degradation caused by nickel ammonia reaction,it is necessary to carry out relevant treatment on the anode of the cell to ensure good thermal decomposition of ammonia in the fuel cell.The support body of tubular cell was prepared by injection molding using gypsum molds.For electrolyte and cathode materials,common materials with good performance were selected.Ni O-YSZ/Ni O-YSZ/SSZ/LSM structure tubular anode supported SOFCs were successfully prepared through impregnation and co sintering methods.The prepared cell electrolyte film was dense and the bonding between each layer was tight.After the cell preparation is completed,seal the cell on a self-made testing device and connect it to the self built cell testing platform.Firstly,change the hydrogen flow rate of the cell to explore the optimal hydrogen flow rate.Through experiments,the maximum power density of the cell was 118.1m W/cm2 at 750 ° C and a hydrogen flow rate of 50 ml/min.Then fix the hydrogen flow rate and change the air flow rate to adjust the ratio of hydrogen to air.Comparing the maximum power density of the cell under different gas ratios,it was found that as the air flow rate increased,the maximum power density of the cell gradually increased.However,when the air flow rate reached 60 ml/min,the power density of the cell decreased to 104.44 m W/cm2.Therefore,a hydrogen flow rate of 50 ml/min and an air and hydrogen flow rate of 4:5 were chosen as the subsequent testing conditions for the cell.After exploring the testing conditions of the cell,the optimal testing conditions were adopted to test the performance of the cell using H2 as the fuel.The cell was tested using 20 ml/min of N2 as the carrier gas,25% of ammonia water,and NH3 as the fuel.At 800 ° C,the power densities of the single cell under H2 and ammonia fuel were245.4m W/cm2 and 123.6 m W/cm2,respectively.The electrochemical performance under hydrogen fuel is superior to that under ammonia fuel,mainly due to the small anodic polarization impedance.When the performance of direct ammonia fuel cells differs significantly from that of hydrogen,research has found that the decomposition of ammonia is more difficult.Therefore,alloy catalysts that catalyze ammonia decomposition are selected to be loaded inside the cells.Modify the anodes of t-SOFC by impregnation method.Apply the prepared impregnation solution to the surface of the cell anode support body,so that the loading amounts of Cu,Fe,and Co are all 1% of the cell mass;The molar ratio of Ni to other metal ions is 1:1.Through comparative testing,it was found that when 25%ammonia gas was used,the highest power density of the loaded Cu and Ni catalyst cell was 139.4 m W/cm2,the highest power density of the loaded Fe and Ni catalyst cell was122.7 m W/cm2,and the highest power density of the loaded Go and Ni catalyst cell was 143.6 m W/cm2.Moreover,at any testing temperature,the highest power density of the Co Ni catalyst was always higher than the other two,Observing the EIS image,it can be seen that the total impedance of Co Ni catalyst is also smaller than the other two at the test temperature.Therefore,the catalytic effect of Co element is stronger than that of Cu catalyst,while the catalytic effect of Fe catalyst is the worst.Therefore,Co catalyst can be used to improve the power density of direct ammonia fuel cells.In order to explore the appropriate proportion of catalyst alloy and prepare catalysts with different Co contents,it was found that when the cell passed through 25%ammonia,the highest power density of the cell was 159.1 m W/cm2 when the ratio of Co Ni catalyst was 3:1;As the proportion of Co in the catalyst increases,the overall maximum power density of the cell also increases accordingly.When the Go Ni ratio is3:1,its power density is generally higher than the maximum power density when the Co Ni ratio is 2:1.Moreover,as the Co content decreases,the maximum power density of the cell begins to decrease at various concentrations of ammonia water.When the ratio of Co Ni is 1:3,the highest power density of the cell at various ammonia concentrations is lower than that of other catalysts with different ratios.The performance degradation of SOFC’s direct ammonia fuel(25-28 vol%,500ml)at a constant voltage of 0.75 V for approximately 58 hours is approximately 9.6%.After 65 hours of cell operation under the same test conditions,the power density of the cell decays by approximately 1.8%.Research has shown that SOFC using ammonia as fuel directly is a simple and promising power generation method.There are 37 pictures,6 tables and 115 references in this thesis.