Award Date

December 2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Committee Member

David Hatchett

Second Committee Member

Kathleen Robins

Third Committee Member

Spencer Steinberg

Fourth Committee Member

Shawn Gerstenberger

Number of Pages

106

Abstract

Polyaniline (PANI) has been extensively studied due to its unique electrochemical properties. The conjugated polymer is conductive with high chemical stability below 100°C, mechanical strength, and large surface area. The applications of PANI have included chemical sensing, corrosion inhibition coatings, light emitting diode and as a substrate for metal composite catalysts. Both chemical and electrochemical methods have been developed and utilized in the synthesis of PANI/metal composites. The simultaneous reduction of aniline and metal precursor produces a composite of PANI encapsulated metal, reducing the active surface area available for catalysis. Alternatively, chemical reduction of the metal precursor into preformed PANI produces deposits at the point of contact with the polymer but offers little control over the amount, dispersion, and size of the metal in the composite catalyst.

A method of electrochemically controlled uptake and reduction of Au and Pd metal precursors into PANI was developed. This method exploits the doping mechanism of polyaniline to distribute the metals throughout the polymer as it is oxidized. Deposition of the metal is achieved through the reduction of the polymer and the simultaneous reduction of the metal anion. The morphology of the composites was evaluated using SEM/EDX analysis. Electrochemically controlled metal oxide formation and reduction confirmed that the surface area of the metal in the composite increased with each deposition scan. Both PANI/Au and PANI/Pd composites proved to be effective catalysts for propanol oxidation.

With an understanding of the deposition processes associated with single metal species, the synthesis of bimetallic PANI/AuPd composites was achieved. Previous work has shown that bimetallic catalysts often have higher catalytic efficiency and reduced poisoning when compared to their monometallic counterparts. Competition of the metals in the deposition process was evaluated by reducing Au and Pd simultaneously. In addition, the effect of deposition order was examined by depositing the metals sequentially. SEM/EDX analysis was used to examine the morphology and composition of all the composites. Metal oxide formation and reduction was used to probe the electrochemically distinct metal species within the polymer. Evidence of alloying was observed for most of the bimetallic composites. Propanol oxidation data showed that the bimetallic composites had higher catalytic efficiency when compared to PANI/Au and PANI/Pd.

Keywords

Alcohol oxidation; Bimetallic; Catalysis; Electrochemistry

Disciplines

Chemistry | Engineering Science and Materials | Materials Science and Engineering

Language

English


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