Materials World Network: Tailoring Electrocatalytic Materials by Controlled Surface Exsolution

非技术性总结：固体氧化物燃料电池（SOFC）是一种高效的装置，用于将储存在一系列燃料中的化学能直接转化为电能。与其他能源转换技术相比，它们固有的高效率导致化石燃料消耗和绿色房屋气体排放更少。 该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，这将提高其效率和长期耐用性，从而有助于加速其商业化。正在研究的特定材料，过渡金属掺杂的钛酸盐和钒酸盐，在暴露于还原条件下时经历结构转变，导致催化活性金属纳米颗粒在其表面上沉淀。 这些金属纳米颗粒催化燃料电池电极中发生的化学反应，从而提高器件性能。这一过程的机制正在确定，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进行合作。这种合作将包括研究生和本科生两个层次的学生交流，这将提高学生的教育，并更好地准备他们成为未来的技术领导者。技术概要：固体氧化物燃料电池（SOFC）具有将储存在一系列燃料中的化学能直接转化为电能的高效装置的潜力。然而，为了实现这种潜力，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，正在研究催化活性过渡金属从电子导电主体氧化物中脱出/溶解，作为调整SOFC阳极催化性能和再生由于烧结或吸附毒物而失去的活性的一种手段。所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的导电钛酸盐和钒酸盐。过渡金属，如镍，铂，或钯，从这些主机氧化物在还原条件下，其依赖于氧化物的组合物和缺陷化学，以及微观结构和电化学性能之间的关系的出溶的机制正在确定。出溶金属纳米颗粒与氧化物表面的相互作用也将被表征，并且在这些研究中获得的洞察力将用于设计出溶金属纳米颗粒高度稳定并且通过奥斯特瓦尔德熟化抗粗化的材料系统。溶解/脱溶循环作为一种原位手段，再生催化活性的工作固体氧化物燃料电池的使用也将进行调查。该项目得到了陶瓷项目和材料研究部特别项目办公室的支持。

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.