Date of Graduation

5-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry (PhD)

Degree Level

Graduate

Department

Chemistry & Biochemistry

Advisor/Mentor

Chen, Jingyi

Committee Member

Durham, Bill

Second Committee Member

Hinton, James F.

Third Committee Member

Heyes, Colin D.

Fourth Committee Member

Tian, Z. Ryan

Keywords

Pure sciences; Applied sciences; Electrocatalysts; Methanol oxidation; Multimetallic nanomaterials; Shape directed nanomaterial growth; Tailoring nanomaterial composition

Abstract

This research focuses on the development of shape-controlled synthesis of Cu NM, Cu-based bimetallic and trimetallic nanostructures, and their electrocatalytic properties for methanol oxidation reaction (MOR). Copper nanomaterials (Cu NM) with specific surface facets can tailor their catalytic activity. Understanding reagents responsible for Cu NM growth is important for morphology-controlled synthesis of the nanostructures. This research studies the halide influence on Cu NM growth and morphology in an oil-based synthesis. The morphology of the Cu NM varies with the halide type (i.e., Cl-, Br-, I-), and the halide concentration. Additionally, the type of Cu precursor also influenced the morphology of the resultant Cu NM.

Select Cu nanostructures were utilized as templates for the formation of bimetallic and trimetallic nanostructures in order to study the composition and morphology influence on the electrocatalytic properties. Binary and ternary core-frame and frame nanostructures, composed of Cu, Pt, and Ru, were developed and their electrocatalytic activity was investigated. Multimetallic, branched core-frame nanostructures were formed by co-reducing Pt and Ru onto the vertices and edges of Cu rhombic dodecahedra. The multimetallic frame nanostructures were formed by etching the coreframe nanostructures. Studies over electrocatalytic activity demonstrated the multimetallic coreframe nanostructures decreased MOR activity, while the multimetallic frame nanostructures enhanced MOR activity and stability, due to the alloying at the frame nanostructure’s surface. Additionally, the incorporation of Ru into these novel frame nanostructures improved resistance towards CO poisoning.

This research also develops multimetallic nanotubes with synthetically tunable surface morphology and platinum content. CuPt nanotubes with smooth and rough surface morphology were developed through the in situ separation of the galvanic replacement reaction and the co-reduction mechanisms, during the alloying process with Cu nanowires. Ru was incorporated into the multimetallic nanotubes forming Cu-Pt-Ru smooth and rough surface structure. The influence of nanotube surface morphology and composition on electrocatalytic activity was investigated, which determined the importance of surface roughness for enhanced MOR activity. Rough nanotubes with Ru increased MOR activity, decreased MOR overpotential, and improved resistance towards CO poisoning. This research provides insight into the effects of nanomaterial composition and structure on electrocatalysis of MOR.

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