Controlled synthesis, characterization, and applications of advanced inorganic nanomaterials

Date of Completion

January 2010

Keywords

Chemistry, Inorganic|Engineering, Materials Science

Degree

Ph.D.

Abstract

This research work focused on developing new synthetic methods for various metal oxide nanomaterials with better control of shapes, sizes, phases, structures, and surface properties compared to conventional methods. These as-produced nanomaterials show promising performance as catalysts, battery materials, and coatings. There are four different focused topics included in this work. ^ The first part presents a unique heteroepitaxy growth of nanostructured rutile oxides using cryptomelane MnO2 (OMS-2). This study was conducted with the purpose of developing a simple, inexpensive, and scaleable route to produce nanoscale complex superstructures potentially as a general method for various metal oxides. Materials like rutile TiO 2 and SnO2, and substrate, OMS-2, were selected in this research due to their similar crystal features in heteroepitaxial aspects. ^ The second part of the research demonstrates a general strategy of tuning net redox potentials to controlled the formation of nanoscale particles and their assembly into hollow structures. Several cobalt oxide species and cerium oxide were studied. The as-produced nanostructured CoOOH material has been used a catalyst and precursor to generate many different nanostructured cobalt oxides, Co3O4 and LiCoO2. These cobalt oxide materials show promising performance as catalysts and battery materials. ^ In the third part of this work, the first successful example of a highly water-tolerant, hydrophobic polymer coating on metal oxide catalysts for CO oxidation was conducted. Studies show that protected catalysts have significantly improved lifetimes than uncoated catalysts under highly humid conditions at low temperatures. The results show that this idea is simple, effective, and general for many different metal oxide catalyst systems. Further optimization of this work can lead to the possibility of applying low-cost metal oxide catalysts in many humid conditions to perform particular catalytic reactions. ^ For the fourth part, a single-step method of preparing the well-ordered organic-inorganic hybrid layered manganese oxide nanocomposites under mild conditions was designed. These synthetic strategies were: (1) rapid redox reaction between Mn2+ and Mn2+ ions under mild conditions; (2) selection of highly self-assembling cetyltrimethylammonium ion (CTA+) for well-ordered layered structures; (3) alkali metal ions (eg. Na+, K+, or Rb+) were totally eliminated since these ions might compete with the intercalation of CTA + ions to reduce the order and spacings of layered structures. ^

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