| With the rapid development of human society, there is a dramatic rise in energy consumption. The traditional energy supply mode and a lot of emissions produced by combustion are not suitable for the sustainable development of today’s society. It is urgent to develop an efficient, clean, economic and safe new energy. The fuel cell is a device that use biomass as raw materials and convert chemical energy to electricity directly. It has high energy density, low pollution emission and a bright future for development. Among all fuel cells, SOFC might be even more promising because of highest operating temperature, perdurable stability of electrolyte and wide adaptability of fuels etc. The properties of component materials and microstructure are essential for higher SOFC performance. In this study, we aimed the preparation and microstructure control of Ni/YSZ anode, through developing a novel co-precipatation method to synthesize nanocomposite particles with high yield and homogeneity distribution for anode preparation. On this basis, the effect of the volume of Ni in microstructure and electrochemical performance of Ni/YSZ anode are also discussed.In order to improve the electrochemical performance of SOFC, we adopted different precipitation methods for the synthesis of Ni O-YSZ composite particles. The experimental results show that the selection in precipitating agents and precipitations can significantly affect the yield and homogeneity distribution of the composite particles. As a precondition of the volume ratio of Ni/YSZ = 1:1 in the final Ni/YSZ anode, we design the ratio of raw materials and adopt NH3·H2O, Na OH and their corresponding buffer solutions as co-precipitation agents to synthesis Ni O-YSZ nanocomposite particles. The sample prepared with NH3·H2O as the precipitation agent resulted in low yield(57%), because Ni2+ and ammonia can form soluble substances which can percolated through the filter; when use Na OH instead, the yield of composite particles can be raised to 87.3%( when use Na OH-NH4HCO3, it is 93%); Na OH as a precipitating agent alone with highly basic conditions(PH > 12) usually obtain the co-precipitation sedimen in the form of hydrated hydroxide which causes a non uniform distribution of componengts and sizes of the product powders; when using Na OH- NH4HCO3, our proposed facile co-precipitation method, the cationic Ni2+ interact with anionic Zr carbonate complex to achieve a uniform sedimentation under relatively neutral conditions(PH = 6.5~8.5) and the as-synthesized powders have a homogeneity distribution.On this basis, we adopted a developed co-precipitation method(Na OH-NH4HCO3) and synthesize composite particles with varying phase contents in anode to explore the impact of the volume amount of Ni on the microstructure and electrochemical properties of anode. The results show that using this method we synthesized highly dispersed composite powders of Ni O and YSZ, though the ratio of raw materials is different. All composite can be pressed and sintered at 1350℃. When the content of Ni is ≥50%, the samples have uniform crystal grains in size(<500 nm), however the samples with 70 vol% Ni in anode exists large grains. And the ASR(RP﹣RO) values of the anode increase from 0.22 Ω·cm2 to 1.35 Ω·cm2 with the Ni volume content in anode varying from 30% to 70%, which is relevant to their microstructure. An appropriate YSZ content could benefit a homogeneous distribution of Ni O and YSZ phase, which result in a finer and uniform porous structure after the reduction of the Ni O, a significantly enhanced TPB length and better electrochemical properties. |
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