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Publication Date

Summer 2013

Degree Type

Thesis - Campus Access Only

Degree Name

Master of Science (MS)

Department

Biomedical, Chemical & Materials Engineering

Advisor

Wenchiang R. Chung

Keywords

Ammonia, Anion exchange membranes, Dendritic, Electrodeposition, Electro-oxidation, Fuel Cells

Subject Areas

Chemical engineering; Chemistry; Materials Science

Abstract

This research focused on the development of low-cost electrodes for the

electrochemical oxidation of ammonia to nitrogen, a reaction that has possible

applications in hydrogen generation, direct ammonia fuel cells, water treatment, and

sensors. Statistical design of experiments was used to help develop an efficient and

scalable process for electrodeposition of platinum with a specific electrochemical

surface area of over 25 m2 /g. Catalyst surface area and activity were evaluated

using cyclic voltammetry, and the material microstructure and morphology were

investigated using x-ray diffraction and scanning electron microscopy. The

synthesized electrodes were found to be active toward the ammonia electrooxidation

reaction, particularly when supporting electrolyte was added. However, supporting

electrolyte was not required in order to oxidize the ammonia. As proof of concept, a

homemade direct ammonia fuel cell employing a commercial anion exchange

membrane was tested at room temperature with gravity-fed fuel and without

supporting electrolyte. At room temperature, with passive reactant supply and

using dissolved oxygen at the cathode, the cell produced about one quarter the

power of a direct methanol fuel cell that used active transport of humidified oxygen

and preheated (50◦ C) methanol. With continued development of the membrane,

cathode and membrane electrode assembly, the passive direct ammonia fuel cell

using anion exchange membrane could have performance similar to the equivalent

direct methanol fuel cell, and it could benefit from many advantages of ammonia

over methanol such as lower cost, higher energy density, and reduced greenhouse gas

emissions.

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