Medium Temperature Operating Solid Oxide Fuel Cells Using Hydrocarbon Fuels

固体氧化物燃料电池（sofc）有望提供高能量转换效率。sofc具有使用碳氢化合物燃料的潜力，碳氢化合物燃料可以在阳极上内部转化为氢或一氧化碳等反应性燃料。为了克服诸如结构材料的降解、电极的烧结和材料选择有限等问题，sofc在中温（700 ~ 800℃）下运行是理想的。本研究项目的目的是为在中温下工作的内转化型sofc开发高性能阳极。我们得到了以下结果。在700 ~ 900℃的SOFC中，掺有少量（8vol .%） Ni纳米粒子的混合导电钐掺杂二氧化铈（SDC）阳极表现出比Ni-SDC陶瓷更高的性能。对Ni分散SDC的微观结构分析表明，纳米级Ni催化剂通过增加活性反应位和降低阳极的电阻抗有效地提高了阳极反应速率。ni分散SDC阳极在800℃和0.6 a cm^<-2>加湿H_2中表现出超过1100 h的长期稳定性能。我们成功地阐明了在长期运行过程中阳极微观结构稳定的机制。ni分散SDC阳极与甲烷在S/C（汽碳比）为1的情况下运行，低于完全蒸汽重整所需的S/C。研究发现，利用阳极放电反应产生的水蒸气，CH_4还能进行重整。可通过增加催化剂用量或改变催化剂的分散性来抑制碳沉积。我们发现Ni （8 vol.%）分散的SDC也被应用于固体氧化物电解电池（SOEC）的阴极，以有效地生产氢气。由ni分散的SDC阴极、La(Sr)CoO_3阳极（SDC夹层）和YSZ电解质组成的SOEC具有较高的性能；在H_2+H2_O（p[H_2]=0.6 atm, p[H2_O]=0.4 atm）和O_2 （1 atm）气氛下，在0.50 A cm^<-2>和900℃下无ir电池电压=1.20 V。少

Solid oxide fuel cells (SOFCs) are expected to provide high energy conversion efficiencies. The SOFCs have a potential of use of hydrocarbon fuels, which can be reformed internally to reactive fuels such as hydrogen or carbon monoxide on the anode. It is desirable to operate SOFCs at a medium temperature (700〜800℃) to overcome problems such as degradation of the construction materials, sintering of electrodes, and a limited choice of materials. The aim of this research project is to develop high performance anodes for the internal reforming-type SOFCs operating at medium temperatures. We obtained the following results.1.Mixed conducting samaria-doped ceria (SDC) anodes with a small amount of Ni nanoparticles (8 vol.%) exhibited a higher performance in SOFC operated at 700-900℃ than that of Ni-SDC cermet. Microstructural analyses of Ni-dispersed SDC showed that nanometer-sized Ni catalysts enhanced the anodic reaction rate by increasing the active reaction sites and lowering the electro … More nic resistance in the anode effectively. The Ni-dispersed SDC anode exhibited a stable performance at 800℃ and 0.6 A cm^<-2> in humidified H_2 for a long term over 1100 h. We succeeded to clarify a mechanism for the stabilization of the anode microstructure during the long term operation.2.The Ni-dispersed SDC anode could be operated with methane at S/C (steam to carbon ratio) of unity, which was lower than that required for complete steam reforming. It was found that CH_4 was reformed additionally by utilizing water vapor formed by the anode discharging reaction. The carbon deposition could be suppressed by increasing the amount of catalysts or changing the kind of catalyst dispersed on the SDC.3.We have found that the Ni (8 vol.%)-dispersed SDC was also applied to the cathode in solid oxide electrolysis cell (SOEC) for efficient production of hydrogen. An SOEC, comprised of Ni-dispersed SDC cathode, La(Sr)CoO_3 anode with SDC interlayer and YSZ electrolyte, exhibited fairly high performance ; IR-free cell voltage=1.20 V at 0.50 A cm^<-2> and 900℃ under the atmosphere of H_2+H2_O(p[H_2]=0.6 atm, p[H2_O]=0.4 atm) and O_2 (1 atm). Less