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Date of Award
Master of Science (MS)
Rider, David A. (Materials scientist)
Emory, Steven R.
Patrick, David L.
This study explored the use of a block copolymer, polystyrene-block-poly(4-vinylpyridine), as a template for the synthesis of platinum-gold bimetallic nanoparticles. The polymer forms spherical micelles in solution which can be cast onto a substrate and subsequently undergo film reconstruction in an orthogonal solvent. The film is then placed into an acidic bath containing varying ratios of K2PtCl6 and KAuCl4 to load metals into the film. The nanoparticles are then formed by a reactive argon ion etch to remove polymer and reduce metal salts to a metal (0) state. The polymer selected had a polystyrene to poly(4-vinylpyridine) ratio of 3:1 to favor particle spacing on the surface and to attempt to control particle size and three different polymers were chosen to study. The polymer was analyzed by scanning force microscopy. The particles were analyzed by scanning force microscopy (SFM), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). Average particle size was found to be approximately 3 nm for all catalysts by TEM since they exceeded the detection ability of the SFM tips used. Bimetallic catalysts showed strong evidence for alloying by CV, XPS, and TEM. Composition of all catalysts was determined by XPS. The catalysts were tested for activity in the methanol oxidation reaction utilizing CV and the oxygen reduction reaction using a rotating ring-disk electrode (RRDE). The gold introduced into the particles showed evidence for resisting carbon monoxide poisoning common for pure platinum in the methanol oxidation reaction. In the case of the oxygen reduction reaction, gold appeared to increase the activity in a couple cases, but mostly it helped increase catalyst selectivity for the direct four electron conversion of oxygen to water over the production of peroxide as an intermediate.
Western Washington University
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Mikkelsen, Kyle, "Block copolymer templated bimetallic nanoparticles for fuel cell applications" (2014). WWU Graduate School Collection. 325.