Design And Characterization Of Ni Doped PBFM As Anode For IT-Solid Oxide Fuel Cells

With the rapid economic development,energy and environmental issues have become increasingly prominent.The developments of new energy sources and new energy conversion technologies are two of the most reliable solutions.SOFCs have attracted much attention for many advantages of high conversion efficiency,low pollution,great fuel flexibility and stable electrolytes.Unfortunately,traditional Ni-based anodes are prone to suffer from carbon deposition and sulfur poisoning under hydrocarbon fuels,causing rapid performance degradation.Developing oxide anodes to substitute for Ni-based anodes is an effective solution,yet oxide anodes usually have the disadvantage of low catalytic activity,especially at intermediate tempretures which are the goal operation temperatures for future SOFCs.And therefore,it is of great significance to explore oxide anode materials with great catalytic activity and high carbon tolerance and sulfur poisoning tolerance at intermediate temperatures.Targeting at this key issue,a new oxide anode of(PrBa)0.95Fe1.9-xNixMo0.1O6-δ is explored in this thesis.the parent oxide with A-site deficiency benefits the stability of anode in hydrocarbon and sulfur containing fuels,and the NiI+substitute promotes formation of nano alloy particles,improving the catalytic activity of anode toward the reforming and oxidation reactions of hydrocarbon fuels.The thesis mainly contains the following three chapters.Chapter 1 first outlines the development and challenges of SOFCs and introduces their classification and working principles.Next the electrolyte and electrode materials for oxygen ion conductor solid oxide fuel cells(O-SOFCs)are mainly introduced and the principle of AC impedance spectroscopy is explained.Finally,the scientific issues that this thesis is going to focus on are prposed.In chapter 2,a series of new oxides,(PrBa)0.95Fe1.9-xNixMo0.1O6-δ(PBFMNix,x=0,0.1,0.2,0.3,0.4),are fabricated,and their physical and chemical characteristics are investigated.Due to the charge compensation mechanism,the ratio of Fe2+/Fe3+ and Mo5+/Mo6+ in PBFMNix decreases with the increased ratio of Ni2+dopant,which helps to depress the formation of an impurity phase(BaMoO4).Meanwhile,the substitution of Ni2+facilitates Fe3+ and Mo6+to be reduced to lower valence(Fe2+ and Mo5+)in reducing atmosphere,and is beneficial to the formation of FeNi3 alloy nanoparticles exsolved from the parent oxides,which greatly accelerates the chemical adsorption and surface reaction kinetics of H2 oxidation,improving the electrocatalytic activity.Transformation of the electrical conduction from p-type to n-type after reduction is also observed.A very small polarization resistance of 0.028 Ω cm2 at 750℃ is achieved for the cell PBFMNi0.3-SDC|SDC|LSCF-SDC in H2 fuel.More importantly,when fueled with propane and sysgas with 50 ppm H2S,the maximum power density of PBFMNi0.3-SDC|SDC|LSCF-SDC single cells at 750℃ is 332 and 498 mW cm-2,respectively,and the cells achieve a short term stability of 50 hours and 100 hours without significant decay in these two fuels.These results suggest that PBFMNi0.3 is a promising SOFC anode material with high-performance at intermediate temperatures.Chapter 3 make a brief summary of the research contents of this paper and find out the areas in the paper that need to be improved and propose directions for further research.