Novel defective oxides: synthesis, properties and applications

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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.