The Preparation And Performance Of Solid Oxide Fuel Cells Alloy Based Anode Materials

Solid oxide fuel cells (SOFCs) are new devices which can convert energy with high efficiency, low pollution and flexibility in the choice of fuels. As a new source of energy, SOFCs are attracting extensive attention and research.Conventional SOFCs which use yttria-stablilised zirconia (YSZ) as electrolyte are usually operated at high temperature in order to obtain good performance, which will cause a series problems such as interfacial reaction, electrode sinter and heat matching. So it is desirable to lower the operation temperature to 500-800℃. It is a important task to develop a high performance anode materials in order to reduce the interfacial resistance and prevent the reaction between the anode and electrolyte, reduce the anode polarization. Huang and his cooperator report a novel double perovskite anode material Sr2Mg1-xMnxMoO6-d which showed better electrochemical performance, this anode material can be used with a wide range of fuels, not only be able to suppress carbon deposition, at the same time has good anti-sulfur performance. Composite anodes such as Cu/CeO2/YSZ were studied by Gorte and cooperator, addition of cobalt or nickel to form alloy based anode was also found to enhance the catalytic activity and the capacity of anti-sintering of the Cu/CeO2/YSZ cermet anode.In this paper, we explore a novel anode material to substitute the Ni based cermet anode for intermediate temperature solid oxide fuel cell based on Samarium-doped ceria (SDC) electrolyte, by developing and investigating transition-metal binary alloys based anodes.Chapter I reviews the types and characteristic of Fuel Cells and solid oxide fuel cell such as the working principle, components, performance requirements, kinetics of anode electrode, and briefly introduce the single-chamber solid oxide fuel cell. The main work and the purpose of research are proposed.Chapter II of this article details the experimental methods and characterization tools. In this paper, the oxide powders and the SDC powders were prepared using the glycine-nitrate synthesis process and mechanically mixed and thoroughly ground as the initial powders of anode material. And the main techniques of characterization were given such as X-ray diffraction (XRD), Van der Pauw DC four-probe method, analysis of thermal expansion, and cyclic voltammetry.The III, IV and V parts of this thesis discussed the preparation and electrochemical properties of the Ni-Cu, Ni-Fe, Co-Fe alloys matrix composite anode materials, respectively. At last, we test and analyse the output performance of single-cell.Binary alloys based anode materials, Ni_1-xCu_x(x=0.05,0.1,0.15,0.2)-SDC, Ni_1-xFe_x(x=0.1,0.15,0.2,0.25)-SDC, Co_1-xFe_x(x=0.2,0.4,0.5,0.6) -SDC, were formed by in situ reduction of Ni_1-xCu_xO_y-SDC, Ni_1-xFe_xO_y-SDC, Co_1-xFe_xO_y-SDC which were preparation and synthesized using glycine-nitrate process and mechanical mixing. XRD results show that these three kinds of anode materials have a good chemical compatibility with electrolyte SDC. The test results of high-temperature conductivity show that the conductive mechanism of the series anode materials has not been changed after reduction, and with electronic conductivity. The coefficient of thermal expansion, Ni_1-xCu_x-SDC composite, is between12.6 15.2 (×10-6K-1). The Ni0.85Cu0.15-SDC anode with thermal expansion coefficient, 12.6814×10^-6K^-1, shows the best matching with SDC (12.4023×10^-6K^-1). And the Ni0.80Fe0.20-SDC (12.3458×10^-6K^-1), Co_0.50Fe_0.50-SDC (12.1967×10^-6K^-1), also have a well matching with electrolyte SDC.The single cells consisted of Ni_1-xCu_x-SDC, Ni_1-xFe_x-SDC, Co_1-xFex–SDC anodes, SDC electrolytes, and Ba_0.5Sr_0.5Co_0.8Fe_0.2O₃-δ-GDC(30wt.%) cathodes were prepared by screen printing method. I-V curves of these cells were measured at temperature from 600 to 800℃. With the Ni_1-xCu_x-SDC anode, the cell which uses Ni_0.90Cu_0.10-SDC as anode shows the highest power density, at 800℃the power density was about 406.80mW/cm² when humidified hydrogen was used as fuel and air as oxidant. With Ni_0.75Fe_0.25-SDC, Co_0.40Fe_0.60-SDC anode, at 800℃the power density were about 372.70 mW/cm², 383.32 mW/cm², respectively.Therefore, the transition metal binary alloy matrix composite anodes have a very good performance, and they are suitable anode material for intermediate temperature solid oxide fuel cell. Especially, Co-Fe alloy matrix composite anode materials reported less currently.Chapter VI of this paper is conclusions and outlook which summarizes the main conclusions of this article, as well as the future direction of work can continue.