直接碳基燃料SOFC核壳结构纤维阳极的构建及性能研究

Using hydrocarbon fuel directly is an impending demand for commercial applications of solid oxide fuel cells (SOFC), which impels the perovskite-type anode attract extensive attention due to the advantage of good resistance to sulfur poisoning and carbon deposition. However, the catalytic activity and mixed ionic-electronic conductivity of perovskite-type anode materials are relatively low. Accordingly it is commonly used in combination with other ionic conductors and/or electronic conductor materials. Obviously, it is of great significance for developing excellent perovskite-type anode to understand how the structure characteristics of the composite anode, such as phase distribution and the phase interface structure, affect its electrochemical performance and long term structural stability. In this proposal, we are attempting to construct core-shell structured nanofiber of LSCM-GDC composite anode, to broaden anode catalytic active area and enhance the mixed ionic-electronic conductivity. The core-shell structured nanofiber will be prepared by combined electrospinning and impregnation methods. The molecular structure of complex precursor will be investigated and adjusted to improve the high temperature structural stability of GDC nanofiber. The electrochemical performance of the core-shell structured LSCM-GDC nanofiber anode directly using hydrocarbon fuel will be tested. Meanwhile, the physical model of mixed ionic-electronic conductivity of the anode will be studied based on neutron powder diffraction analysis and first principle calculations. Also, the phase compositions, molecular structure, and valence of elements at catalytic active area will be probed to reveal the mechanism of catalytic reaction at the anode, and the effects of core-shell microstructure on the enhanced mixed ionic-electronic conductivity and electrochemical catalytic activity of LSCM anode will be clarified.

能够直接使用碳基燃料是固体氧化物燃料电池(SOFC)商业化发展的切实需求，使具有耐硫、抗积碳性能优势的钙钛矿型阳极的开发备受关注。但钙钛矿型阳极材料催化活性和混合导电性能偏低，常与其它离子导体或电子导体材料复合使用。对复合阳极相分散度、相界面结构等亚微结构特征影响电极性能的规律及机制的理解，对于开发高性能、稳定的钙钛矿阳极意义重大。本项目提出构建核壳结构纳米纤维复合阳极，增大阳极催化活性区域和优化离子、电子传导路径的思想。采用静电纺丝工艺结合浸渍法制备相分散度高的核壳结构纳米纤维LSCM-GDC阳极，通过前驱络合分子结构调控改善纤维耐高温性能。测试该阳极的电化学性能，结合电子和氧离子输运特性的衍射分析和模拟计算建立混合导电模型。对阳极催化活性区域的物相、分子结构、元素形态、化合价态等进行多手段表征，揭示阳极催化机理，重点阐明核壳显微结构对LSCM阳极混合导电性能和催化活性的增强作用及机制。

能够直接使用碳基燃料是固体氧化物燃料电池(SOFC)商业化发展的切实需求，开发具有耐硫、抗积碳性能优势的钙钛矿型阳极势在必行。但钙钛矿型阳极材料催化活性和混合导电性能偏低。本项目通过构建纳米纤维结构La0.75Sr0.25Cr0.5Mn0.5O3-δ（LSCM）基阳极，改善阳极结构，优化电子和离子传导路径，增大阳极催化活性区域，从而提高了钙钛矿阳极的电化学性能，并对LSCM纤维高温结构稳定性的影响因素、影响机制和改善方法进行了探讨。具体工作包括：探索和优化了LSCM纤维的静电纺丝制备工艺；分析了金属-有机络合分子形态对静电纺丝纤维形貌和高温结构稳定性的影响，创造性提出了通过络合剂分子量级配调控金属-有机络合分子形态从而改善无机材料静电纺丝纤维高温结构稳定性的新方法，在此基础上优化了LSCM静电纺丝液的配方，将LSCM的耐受温度提高了150℃以上；分析了静电纺丝工艺的纤维形成机制，研究了纺丝液中表面活性剂对纤维产物形貌的影响；通过浸渍GDC和Ni相增大了LSCM纤维阳极的催化反应活性区域，改善了电极的催化活性，尤其是解决了纤维间固相接触点（面）不足的问题，从而进一步提高了电池的电化学输出性能。该项目的实施为今后继续发展完善纤维结构SOFC阳极奠定了技术基础和提供了理论借鉴。