无CO2排放的直接甲烷SOFC复合阳极体系的构建及其电/芳烃共生行为研究

As of today, researchers and scientists in Solid Oxide Fuel Cells (SOFCs) community have done intensive work on improving the anode performance in methane with respect to using the natural gas, which is easy available and accessible, as the fuel for SOFCs. However, the currently popular perovskite anode and the conventional Ni/YSZ anode are compromised by lower catalytic performance and vulnerability to carbon deposit respectively when fueled with methane. Under these circumstances, a novel anode system is put forward in this proposal with regard to improving the anode performance and the long-term durability usually resulted from either by carbon deposit or sulfur contamination for the conventional anodes. In this proposed anode, the nonoxidative methane dehydroaromatization (MDA) as an nonoxidative coupling reaction of methane is introduced in order to activate the methane dehydrogenation processes. In this project, the cell will be fabricated by tape casting method on basis of BaZr(Ce)O3 based electrolyte which is characteristic with both proton conducting and oxygen ion conducting capacity at high temperature. In our anode, the Mo based molecular sieve MDA catalyst layer and LaFeO3 (SrTiO3) based anode layer will be fabricated by solution impregnation method and the composition and structure of the materials will be optimized according to the performance during the test. This research will focused on the electrode processes of LaFeO3 (SrTiO3) based anode with Mo based molecular sieve MDA catalyst. The strengthening mechanism of MDA processes and selective oxidation behavior of hydrogen in the anode as well as the carbon deposit and polyaromatic hydrocarbon (PAH) as the undesired side products during the MDA processes will be investigated before and after the operation of the cell. The performance of the cell with this composite anode at different temperatures will be measured and the focus will be put on the performance at different current densities because different current density means different water generation in the anode, which is crucial for the carbon and PAH removal. The less carbon and PAH in anode, the more stable the anode behaves using the methane as the fuel. Another important research in the project is about the sulfur tolerance behavior of the anode in the fuel in the presence of H2S in it. Therefore, in this project, the sulfur tolerance of the anode is about to be studied through comparing the changing of the performance of the anode before and after addition of H2S in the fuel and characterizing the material composition and structure by using the TEM, XPS, XRD and Raman spectroscopy. In summary, it is reasonable to believe that the novel anode materials with high anode performance based on MDA catalyst and the relationship between microstucture and performance will be obtained in this project. Based on the studies mentioned above in this project, the direct methane anode with durable performance and free from CO2 emission is being expected to be operating with electricity and arene generated concurrently.

本项目针对传统的镍基阳极积碳硫毒化问题及钙钛矿阳极催化活性差的问题，设计构建了新型的直接甲烷SOFC阳极体系：借助甲烷非氧化耦合反应中的甲烷脱氢芳构化(MDA)过程构建新型直接甲烷SOFC阳极体系，利用BaZr(Ce)O3基电解质材料的质子导电特性强化MDA过程，实现甲烷到电能和芳烃的转化。本项目将采用流延法制备BaZr(Ce)O3基阳极支撑型电池，通过浸渍法构建Mo基分子筛MDA催化层及LaFeO3(SrTiO3)基阳极层并优化材料的组成和结构。研究中将重点考察电极过程中MDA催化层中的甲烷转化强化机制和及LaFeO3(SrTiO3)基阳极中氢气的选择性氧化行为；弄清电解质的氧离子导电特性对电池阳极中积碳和杂环芳烃（PAH）分解行为的影响规律；阐明燃料气中微量H2S对电极过程毒化行为及微观机制；通过优化材料组成和结构得到能稳定高效运行的新型无CO2排放的电/芳烃共生的阳极体系。

本项目针对传统的镍基阳极积碳硫毒化问题及钙钛矿阳极催化活性差的问题，设计构建了新型的直接甲烷SOFC阳极体系：借助甲烷非氧化耦合反应中的甲烷脱氢芳构化(MDA)过程构建新型直接甲烷SOFC阳极体系，利用BaZr(Ce)O3基电解质材料的质子导电特性强化MDA过程，实现甲烷到电能和芳烃的转化。经过四年的研究，本项目获得了电解质BZCYYB4411新型制备及烧结工艺，得到了18微米厚致密电解质，烧结温度由1550oC降低到了1400oC，成功通过浸渍涂敷-共烧结法制备出具有高致密度电解质的阳极支撑电池片。得到了A位缺位量x分别为0、3%、5%、7%、9%的La0.3Sr0.7Ti0.3Fe0.7O3-δ阴极材料粉体，即LSTF(La0.3Sr0.7)1-xTi0.3Fe0.7O3-δ（LSTF-x，x=0、3%、5%、7%、9%）。并利用了一系列表征手段研究了不同A位缺位量对LSTF物相结构和电化学性能的影响。获得的Mo离子改性HTNU-9催化剂在甲烷无氧芳构化反应中表现出了很好的催化活性和稳定性。HTNU-9/LSTF0.7-BZCYYb|BZCYYb|LSM-BZCYYb单电池在850、800、750℃时，峰值功率密度分别为829、659、492 mW/cm2，甲烷转化率分别为23%，18%和15%，远高于国内外的同类研究结果。电池在 50mA/cm2的电流密度下运行100h，阳极无明显积碳。因此，本项目得到的HTNU-9/LSTF0.7-BZCYYb|BZCYYb|LSM-BZCYYb电池成功实现了甲烷到苯的转化，表现出了高的放电性能和稳定性，实现了放电中无CO2排放的目标。研究中得到的电池制备方法、钙钛矿电极材料、分子筛甲烷转化催化剂以及高性能单电池是本项目的重要进展，电池显示出的关于甲烷到苯的高转化率以及高的放电性能对于甲烷高效转化、扩展燃料电池技术应用场景具有重要意义。