Title

Synthesis, characterization, and applications of nano-functional transition metal oxides materials and graphite anode modified by CVD carbon coating

Date of Completion

January 2008

Keywords

Engineering, Materials Science

Degree

Ph.D.

Abstract

This research consists of two major sections. The first section of this research is focused on developing novel synthesis methods, characterization, and catalytic applications of multi-functional transition metal oxides including manganese oxide nano-materials (2x2 tunel structured manganese oxide octahedral molecular sieve), 3D hierarchical nano-architecture ϵ-MnO2 and cobalt oxides, and cobalt based materials. Manganese oxide octahedral molecula sieves (OMS) have ID open framework structures with various theoretical nano-scale tunnel size materials have been investigated extensively as low cost and environmentally benign ionic and molecular sieves and efficient redox catalysts. A novel and efficient solvent-free method has been developed to synthesize manganese oxides with 2 x 2 tunnel structures. The properties of the synthesized OMS-2 materilas have been compared with that synthesized by conventional reflux and hydrothermal methods. Epsilon manganese dioxides with controlled novel 3D architectures have been fabricated via a hydrothermal chemical reaction. The effects of reaction time and reaction temperature on the morphology of the final ϵ-MnO2 are investigated, and the formation mechanisms of the hierarchical nano-architectures are proposed. The magnetic properties of ϵ-MnO2 are also studied. Resides manganese oxides, a microwave-heating reflux route has been used to synthesize 3D flower like cobalt hydrotalcite-like compounds with layered structure and these compounds can be transferred into spinel structure of Co3O 4. Both materials show the electrocatalytic activity and stability for the electrochemical reduction of oxygen. Therefore these materials have the potential to be electrocatyltic catalysts. ^ The second section of the research is to study the microstructure of carbon films coated on the iron and graphite particles by a Chemical Vapor Deposition (CVD) method and the relationship between the microstructure of the carbon coatings and their effects on electrochemical properties. ^