碳基燃料反应特异性及阳极催化动力学研究

孙春文

摘 要：研究可以直接电化学氧化碳氢化合物燃料的新型阳极和外重整器是研制碳基燃料固体氧化物燃料电池的核心。

该研究发展了一种制备微纳结构花状氧化铈的新方法，负载镍后是一种性能优良的低温甲烷部分氧化和水汽重整催化剂，通过调整合适的CH4/O2比或水蒸汽/碳（S/C）比可以有效地抑制积碳；甲烷水蒸汽重整可以在较低温度（550 ℃）下发生，590 ℃时催化剂的使用寿命超过1 000 h，转化率超过80%；设计、制作了单室甲烷水蒸气重整反应器和500 w叠片式甲烷水蒸气重整反应器，性能稳定。

首次利用先进的球差校正扫描透射电镜（STEM）和同步辐射X射线吸收谱（XAS）技术对双钙钛矿结构Sr2CoMoO6在不同气氛下的结构演变进行了研究，发现在高温还原性气氛下，Sr2CoMoO6中会形成大量氧空位，制备的一体化电池SCMO-LSGM/LSGM/SCCO-LSGM在850 ℃下输出功率密度达到1.63 W/cm2，SCMO作为电极制备的对称电池在650 ℃下稳定工作100 h。用溶胶-凝胶法制备了多孔核壳结构的Sr0.88Y0.08TiO3（YST）-Ce0.8Sm0.2O1.9（SDC）复合材料，研究结果表明YST@SDC复合阳极具有优异的抗积碳性能，是一种有希望的碳氢化合物燃料基SOFCs的阳极材料。利用同步辐射真空紫外-分子束质谱（SR-MBMS）原位技术，首次研究了碳氢化合物甲烷、乙烯、丁烷、异辛烷等在SDC浸渍的Ni基阳极上的催化裂解机理。发现纳米阳极降低了CH4裂解温度、具有高的催化活性。通常认为乙烯在催化剂上的积碳速度非常的快，分子束质谱分析发现在浸渍SDC纳米粒子的阳极上生成了乙烯，但实验没有观察到积碳，说明SDC浸渍的Ni基阳极是非常抗积碳的。

该研究为发展抑制积碳的新方法提供了思路。最先研究了钙钛矿Sr1-xCexCoO3-delta（x：0.05～0.15）用于中低温SOFC阴极材料，显示出优异的氧还原特性，在700 ℃下，30 wt.%SDC和SCCO005形成的复合阴极的电池输出功率密度高达1.01 W/cm2；利用中子粉末衍射研究了其不同组分的结构，很好地与性能关联起来，相关工作已申请了两项中国发明专利。

关键词：固体氧化物燃料电池 阳极 碳氢化合物 重整 反应动力学

Abstract：Alternative anodes that can directly electrochemical oxidation of hydrocarbon fuels and reformers are two key technologies to develop carbon-based solid oxide fuel cells （SOFCs）. The structural evolution of double-perovskite Sr2CoMoO6（SCMO） during reduction/oxidation treatment was firstly clarified by means of XRD， XAS and STEM. Reduction causes oxygen vacancies and oxygen disordering，and lowers the average valence state of Mo for charge balance.Furthermore， Sr2CoMoO6 has been investigated as electrodes for SOFCs.The peak power density of a La0.9Sr0.1Ga0.8Sr0.2O3（LSGM） monolith supported cell is up to 1634 mW cm-2 at 850℃. The peak power density of a symmetrical fuel cell SCMO-LSGM/LSGM/SCMO-LSGM reaches 700 mW cm-2 at 850 ℃. The cell shows excellent long-term stability at 650 ℃ for more than 100 h. These results demonstrate that SCMO is a promising alternative material as anode for low-temperature solid oxide fuel cells as well as both electrode materials for symmetrical SOFCs. A porous Sr0.88Y0.08TiO3（YST）-Ce0.8Sm0.2O1.9（SDC）composite with a core/shell structure has been prepared with a sol-gel method and evaluated as an alternative anode for SOFCs.When CH4 was used as fuel， the peak power density of the single cell reached about 150 mW cm-2 at 900 ℃. It demonstrates that YST coated SDC composite is a promising alternative anode for SOFCs with hydrocarbon fuels. The molecular-beam spectrometric technique coupled with tunable synchrotron vacuum ultraviolet photoionization is applied to reveal the catalytic mechanism of methane over Ni-based anodes with and without impregnated nano-sized SDC particles.It indicates that the impregnated SDC nanoparticles are highly catalytically active for methane decomposition.C2H4is observed when the impregnated Ni-SDC composites are used as the catalyst，suggesting that SDC coating also suppresses carbon deposition at the anodes of SOFCs.Perovskite Sr1-xCexCoO3-delta（x：0.05～0.15） have been prepared by a sol-gel method and studied as cathodes for IT-SOFCs.Sr1-xCexCoO3-delta materials have sufficiently high electronic conductivities and excellent chemical compatibility with SDC electrolyte.At 700℃，the peak power density of cells with Sr0.95Ce0.05CoO3-delta is 0.625 W cm-2 By forming a composite cathode with 30 wt.%SDC， the peak power density of the cell reaches 1.01 W cm-2 at 700 ℃，better than that of Sm0.5Sr0.5CoO3-based cathode.This demonstrates that Sr1-xCexCoO3-delta（x：0.05～0.15）-based materials are promising cathodes for an IT-SOFC.Key Words：Solid oxide fuel cells；Anode；hydrocarbon fuels；Reforming；Kinetics of reactions

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