铁铬基钙钛矿体系阴极材料的性能调控与催化活性机理研究

Newly-developed chromium ferrite perovskite-type complex oxides accommodate the dual peculiarities of robust redox stability and high catalytic activity towards oxygen reduction. These desired properties make them promising candidate materials for cathode of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Currently, how to realize a compromise among various properties of chromium ferrite perovskite-type cathode materials remains as a challenge. Meanwhile, the origin of the high catalytic activity emerges as an intriguing issue of great importance. The applicants of this project plan to regulate the properties of chromium ferrite perovskite-type cathode materials by employing an A–site composition design strategy. The emphases are aimed at exploring effective approaches to an overall improvement of the properties of chromium ferrite perovskite-type cathode materials and understanding the underlying mechanisms of the property improvement. The structural evolution and property variation of chromium ferrite perovskite-type complex oxides with composition change will be surveyed. Relations between the property variation and structural evolution will be investigated in detail. Essential factors contributing to the mixed electronic-ionic conduction, thermal expansion and catalytic activity will be elucidated in view of the structural evolution. The origin of the catalytic activity in chromium ferrite perovskite-type complex oxides will be explicated from a structural viewpoint. Based on these efforts, it is expected that the overall properties of chromium ferrite perovskite-type cathode materials could be modified. This study will help to better understand the fundamental aspects of the perovskite-type cathode materials, such as inherent relevance between the properties and multi-level structures. The outcomes resulting from this study will serve to be new contributions to the knowledge of materials science and solid state ions, which will in turn offer a guideline for further development of advanced cathode materials for IT-SOFCs.

Fe-Cr基钙钛矿结构复合氧化物兼有强的氧化还原稳定性和优良的对氧还原催化活性，为发展高性能的中温固体氧化物燃料电池（IT-SOFC）阴极材料提供新的前景。实现Fe-Cr基钙钛矿阴极材料的性能协调和认清其阴极催化活性的起源是亟待解决的问题。本项目通过A位组成设计进行Fe-Cr基钙钛矿结构阴极材料的性能调控，探索优化其综合性能的有效途径与机制。本项目研究Fe-Cr基钙钛矿体系的结构和性能随组成的变化，围绕对钙钛矿结构复合氧化物阴极材料的性能与不同层次结构的内在关联这个基本问题的研究，揭示影响Fe-Cr基钙钛矿体系的混合导电特性、热膨胀性能和阴极催化性能的本质因素，阐明该体系阴极催化活性的本源，在此基础上实现该体系性能的合理调控，研制出综合性能优良的Fe-Cr基钙钛矿结构阴极材料。本项目的研究丰富材料科学和固态离子学的知识体系，为发展高性能的IT-SOFC阴极材料提供科学依据和指导。

Fe-Cr基钙钛矿混合导体是中温固体氧化物燃料电池（IT-SOFC）阴极的新型候选材料。本项目研究Fe-Cr基钙钛矿复合氧化物的A位组成对其晶体结构、氧的非化学计量、导电性能、热膨胀性能和对氧还原反应的电催化性能的影响，探究Fe-Cr基钙钛矿复合氧化物的各项性能变化与其结构变化之间的相关性，分析Fe-Cr基钙钛矿多孔阴极的电催化活性的起源，并研制具有优良综合性能的Fe-Cr基钙钛矿阴极材料。.取得以下主要研究结果。（1）探索出适用于制备不同A位组成Fe-Cr基钙钛矿粉体的化学法合成工艺，制备出Fe-Cr基钙钛矿的超微细粉体，为控制多孔阴极的显微结构提供了技术基础。（2）通过调节Fe-Cr基钙钛矿A位离子半径，对其晶体结构进行调控，实现了其导电性能和热膨胀性能的综合优化。（3）探明了各电极反应过程对Fe-Cr基钙钛矿多孔阴极的极化电阻的贡献，确定了Fe-Cr基钙钛矿多孔阴极在阴极极化作用下的电化学活化机制，揭示了Fe-Cr基钙钛矿多孔阴极具有优良电催化活性的结构起源。（4）通过合理调控Fe-Cr基钙钛矿多孔阴极的厚度，实现各电极反应过程在动力学上的协调与匹配，显著优化了其电催化性能。（5）在本项目研究的Fe-Cr基钙钛矿中，La0.3Ca0.7Fe0.7Cr0.3O3-δ具有最佳的综合性能，在IT-SOFC阴极方面具有应用前景，其平均热膨胀系数为~11×10-6 K-1（50-1000 °C），电导率为~40 Scm-1 (600-800 °C），其多孔阴极的极化电阻为~0.06 Ωcm2 (800 °C)，以La0.3Ca0.7Fe0.7Cr0.3O3-δ为阴极的阳极支撑型单电池在800 °C和H2燃料条件下的最大输出功率密度为1228 mW•cm-2。.基于以上研究结果，在国际、国内学术期刊上发表13篇论文，获得1项国家发明专利的授权。