Novel defective oxides: synthesis, properties and applications

我的研究计划的总体长期目标是在分子水平上了解复杂的、通常是有缺陷的无机材料的性质和化学转化。我们努力建立结构-反应性关系，以指导材料设计以提高性能、降低运营成本和提高可靠性。在能源和环境研究的框架下，该研究计划旨在获得对(电)催化剂在操作过程中的分子水平的了解，并开发用于发光和磁性应用的材料特性。所选择的材料是自然界中普遍存在的有缺陷的氧化物。这些材料价格便宜、容易获得或可合成，并且具有可调性能，有可能解决许多工业和技术问题。 在氧化物材料的众多晶体家族中，钙钛矿通过微调氧化物的化学成分，提供了一个独特的机会来创造所需物理性能的材料。由此产生的氧化物性质可能会发生巨大变化，例如，钙钛矿可以表现出离子导电性、电子导电性或仅仅是绝缘体。氧化物结构的复杂组成和典型的缺陷性质提供了材料本身(氧化态、表面物种、分离和相形成、纳米域性质等)以及涉及的反应和机理方面的丰富化学成分。 钙钛矿基催化剂在环境、工业和绿色能源领域已被提出作为传统贵金属基催化剂的替代品。这项研究计划的短期目标是了解化学结构如何影响催化剂化学性质的基本原理，并应用这些知识来提高这些催化剂的效率、电阻率和可操作性。为此，将采用溶胶-凝胶法或活性混合法合成钙钛矿结构，对其晶体结构、导电性和稳定性进行充分表征，并在自制系统中对其催化性能进行评价。在这项建议中，我们将以最近合成掺杂铁氧体的经验为基础，开发新的钙钛矿族，具体侧重于三个应用： 1)离子-电子混合导电钙钛矿将被用作固体氧化物燃料电池阳极和气体传感器。一种高效的低温固体氧化物燃料电池阳极将极大地降低工厂平衡的工程成本，从而使该行业发生革命性的变化。 2)氧化还原不稳定的钙钛矿将成为催化应用的目标。将研究两种类型的反应，挥发性有机化合物的氧化和光催化分解水。这两种催化应用在世界范围内都具有极其重要的环境和经济价值。 3)高自旋原子掺杂的钙钛矿材料将被开发用于光致发光和磁性应用。例如，掺Dy+3有望增强这两种性能。通过对浓度、微区尺寸和微结构的适当控制，可以合成出强光致发光和阴极发光材料，从而直接影响平板显示器和存储器的应用。

The general long term objective of my research program is to understand, at the molecular level, the properties and chemical transformations of complex, usually defective, inorganic materials. We strive to establish structure-reactivity relationships that guide material design for increased performance, reduced operating cost, and improved reliability. The research program, under the umbrella of energy and environmental research, aims to obtain a molecular-level understanding of (electro)catalysts during operation and to exploit the material properties for luminescence and magnetic applications. The chosen materials are defective oxides ubiquitous in nature. Being cheap, readily available or synthesizable, and with tunable properties, these material have the potential to solve many industrial and technological problems. Among the many crystal families of oxide materials, perovskites offer a unique opportunity to create materials of the desired physical properties by fine-tuning the chemical composition of the oxide. The resulting oxide properties can change dramatically, for example perovskite can show ionic conductivity, electronic conductivity or simply be insulators. The complex compositions and typically defective nature of the oxide structure offers a rich chemistry both in terms of the material itself (oxidation states, surface species, segregation and phase formation, nano-domain properties, etc) and the reactions and mechanisms involved. Pervoskite-based catalysts have been proposed as alternatives to traditional noble metal-based catalysts in the fields of environmental, industrial and “greener” energy. The short term goals of this research program are to understand the fundamentals of how the chemical structure impacts the chemical properties of the catalysts and applying this knowledge to increase the efficiency, resistivity, and operability of these catalysts in “real-world setting”. To this end, the perovskite structures will be synthesized by sol-gel or active mixing methods, fully characterized as to their crystal structure, conductivity and stability, and their catalyst performance will be evaluated in home built systems. In this proposal we will build upon recent experience in the synthesis of doped ferrites to develop new families of perovskites with specific focus on three applications: 1) Mixed ion-electron conducting perovskites will be sought after for use as solid oxide fuel cell anodes and gas sensors. An efficient anode for LT-SOFCs will revolutionize the industry by lowering the engineering costs of balance of plant dramatically. 2) Redox labile perovskites will be targeted for catalytic applications. Two types of reaction will be studied, the oxidation of volatile organic compounds and the photocatalytic splitting of water. Both of these catalytic applications have an extremely important environmental and economic value worldwide. 3) Perovskites doped with high spin atoms will be developed for photoluminescence and magnetic applications. Doping with Dy+3 for example is expected to enhance both of these properties. With appropriate control of concentration, domain size and microstructure, strong photoluminescent and cathodeluminescent materials can be synthesized to directly impact applications of flat panel displays and memory storage.