Date of Award

5-27-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Applied Science

First Advisor

Tito Viswanathan

Abstract

An alternative for depleting fossil fuel resources would be the development of fuel cells, batteries and solar cells. The current project aims at development of the cathode electrode material for alkaline fuel cells which is utilized for the reduction of oxygen to water. A simple, highly efficient, and rapid microwave method for the synthesis of doped carbons from different precursor sources like tannin, aminated tannin and tannin-melamine-hexamine has been developed. Different dopants include phosphorus, nitrogen, oxygen, sulfur and silicon. The method uses no inert or reducing gas during the transformation. Yields resulting from this particular technique are as high as 46%. Elemental analysis from XPS studies have confirmed the heteroatom doping of carbon. Scanning Electron Microscopy has shown that the formation of doped carbons with different morphologies. BET surface area of the materials are found to be as high as ~1150 m2/g and exhibit both microporous and mesoporous structure. All the materials show significant promise in oxygen reduction reactions for alkaline fuel cells. Electrochemical methods of analysis like cyclic voltammetry, rotating disk electrode and rotating ring disk electrode studies were used to analyze the mechanism of oxygen reduction reaction Gas sensors available in the market are based on semiconductor metal oxides but the main drawback includes high temperature operating conditions. A profound amount of research is focused on the development of gas sensors from conducting polymers-metal oxide composites, because of their ease of preparation, high surface and gas sensitivity at room temperature conditions. Among different conducting polymers, polyaniline is unique because of its doping chemistry and can be used to detect a wide variety of gases. The current dissertation reports the use of tanninsulfonic acid as a dopant to synthesize-polyaniline-metal oxide composites to detect ammonia gas. Tanninsulfonic acid doped polyaniline-titanium dioxide or aluminum oxide nanocomposites were synthesized by in situ polymerization of aniline in the presence of tanninsulfonic acid with varying amounts of metal oxides. X-ray diffraction, UV-Visible, infrared spectroscopy as well as SEM imaging along with (Energy Dispersive X-Ray Analysis) EDAX was used to characterize the composites. AFM was used to analyze the surface roughness of the polyaniline-metal oxide composite thin films. Gas sensors were prepared by spin coating tanninsulfonic acid dopedpolyaniline-TiO2orAl2O3 composites onto glass slides, and gas sensors were tested for different concentrations of ammonia gas at room temperature conditions by sensing the changes in surface resistivity of the films with respect to time.

Download

Included in

Chemistry Commons

Share

COinS