Materials World Network: Tailoring Electrocatalytic Materials by Controlled Surface Exsolution

非技术概述：固体氧化物燃料电池（SOFC）是一种将储存在各种燃料中的化学能直接转化为电能的高效装置。与其他能源转换技术相比，其固有的高效率导致较少的化石燃料消耗和温室气体排放。这个材料世界网络项目的重点是开发一种用于SOFC电极的新型材料，这将提高它们的效率和长期耐用性，从而有助于加速它们的商业化。正在研究的特定材料，过渡金属掺杂钛酸盐和钒酸盐，在暴露于还原条件下会发生结构转变，导致在其表面上沉淀催化活性金属纳米颗粒。这些金属纳米颗粒催化发生在燃料电池电极中的化学反应，从而提高设备的性能。这一过程的机制正在被确定，这一见解将用于设计具有最佳性能的电极成分和微观结构。美国宾夕法尼亚大学和英国圣安德鲁斯大学的研究人员将在该项目上展开合作。这项合作将包括研究生和本科生的学生交流，这将加强学生的教育，并为他们成为未来的技术领导者做好更好的准备。技术概述：固体氧化物燃料电池（SOFC）具有将储存在各种燃料中的化学能直接转化为电能的高效装置的潜力。然而，为了实现这一潜力，需要在SOFC操作条件下稳定的电催化材料。在这个材料世界网络项目中，正在研究将催化活性过渡金属从电子导电的主氧化物中析出/溶解到电子导电的主氧化物中，以此来调整SOFC阳极的催化性能，并再生由于烧结或吸附有毒物质而失去的活性。研究的具体材料体系包括具有钙钛矿结构的过渡金属掺杂导电钛酸盐和钒酸盐。在还原条件下，过渡金属（如Ni、Pt或Pd）从这些主氧化物中析出的机理，其对氧化物成分和缺陷化学的依赖，以及微观结构与电化学性能之间的关系正在被确定。此外，还将对溶解的金属纳米颗粒与氧化物表面的相互作用进行表征，并将在这些研究中获得的见解用于设计材料系统，使溶解的金属纳米颗粒高度稳定，并能抵抗奥斯特瓦尔德成熟过程中的粗化。还将研究使用溶解/溶出循环作为原位手段来再生工作sofc的催化活性。本项目由陶瓷项目和材料研究部特别项目办公室资助。

NON-TECHNICAL SUMMARY: Solid oxide fuel cells (SOFC) are highly efficient devices for the conversion of the chemical energy stored in a range of fuels directly into electrical energy. Their inherent high efficiency results in less fossil fuel consumption and green house gas emissions compared to other energy conversion technologies. This Materials World Network project focuses on the development of a novel class of materials for use in the electrodes in SOFC that will increase both their efficiency and long-term durability, which will in turn help to hasten their commercialization. The specific materials that are being investigated, transition metal doped titanates and vanadates, undergo structural transformations upon exposure to reducing conditions that result in the precipitation of catalytically active metal nanoparticles on their surfaces. These metal nanoparticles catalyze the chemical reactions that take place in the fuel cell electrodes, thereby improving the device performance. The mechanism of this process is being determined and this insight will be used to design electrode compositions and microstructures with optimal properties. Researchers at the University of Pennsylvania in the US and the University of St. Andrews in the United Kingdom will collaborate on the project. This collaboration will include student exchanges at both graduate and undergraduate levels that will enhance the students' education and better prepare them to be the technological leaders of the future. TECHNICAL SUMMARY: Solid oxide fuel cells (SOFC) have potential as highly efficient devices for the conversion of the chemical energy stored in a range of fuels directly into electrical energy. Electrocatalytic materials that are stable under SOFC operating conditions are needed, however, for this potential to be realized. In this Materials World Networ project, exsolution/dissolution of catalytically active transition metals out of and into an electronically conducting host oxide is being investigated as a means to tailor the catalytic properties of SOFC anodes and to regenerate activity that is lost due to sintering or adsorption of poisons. The specific materials systems under investigation include transition metal doped conducting titanates and vanadates which have the perovskite structure. The mechanism of the exsolution of transition metals, such as Ni, Pt, or Pd, from these host oxides under reducing conditions, its dependence on the oxide composition and defect chemistry, and the relationships between microstructure and electrochemical performance is being determined. The interaction of the exsolved metal nanoparticles with the oxide surface will also be characterized and the insight obtained in these studies will be used to design materials systems for which the exsolved metal nanoparticles are highly stable and resistant to coarsening via Ostwald ripening. The use of dissolution/exsolution cycles as an in situ means to regenerate catalytic activity in working SOFCs will also be investigated. This project is supported by the Ceramics Program and Office of Special Programs, Division of Materials Research.