Date of Graduation

7-2015

Document Type

Thesis

Degree Name

Master of Science in Chemistry (MS)

Degree Level

Graduate

Department

Chemistry & Biochemistry

Advisor

Jingyi Chen

Committee Member

Ingrid Fritsch

Second Committee Member

Feng Wang

Keywords

Applied sciences; Electrocatalysis; Nanostructure; Pd

Abstract

Pd and its alloys are alternatives of Pt as promising catalysts and electrocatalysts for many reactions. Size controlled synthesis of nanoparticles remains a major research subject, since smaller size particles show better catalytic performance. In this work, we developed a modified chemical wet method to prepare Pd and Pd-Cu nanostructures with uniform small size. Different sizes and shapes of Pd nanostructures were successfully synthesized by using the two reducing agents (i.e., L-ascorbyl-6-palmitate or phenylphosphinic acid). The reducing agents play a role to control the final morphologies and sizes of particles. The use of L-ascorbyl-6-palmitate favors to form irregular branch shapes or rods; in contrast, the use of phenylphosphinic acid tends to form spherical nanoparticles. Furthermore, phenylphosphinic acid can assist with size control of Pd particles. Co-reducing Pd and Cu precursors can obtain Pd-Cu nanostructures with different sizes and shapes. The growth mechanism is followed the deposition of Cu on Pd seeds which are reduced prior to Cu. Similar to pure Pd synthesis, phenylphosphinic acid reduced the precursors to form small uniform spherical particles compared to L-ascorbyl-6-palmitate. It was also found that the composition could also be tuned by using different reducing agents. The catalytic activity of Pd and Pd-Cu nanostructures for ethanol oxidation reaction (EOR) has been tested in basic solution for alkaline fuel cell applications. The specific areas of these Pd and Pd-Cu are much higher than those reported previously. It was found that both Pd and Pd-Cu nanostructures exhibited enhanced catalytic activities and to some extent resisted CO-like intermediates poisoning. Most catalysts had enhanced current densities after 500 cycle scan, indicating enhanced stability of those catalysts.

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