| Summary: | 博士 === 國立交通大學 === 材料科學與工程系所 === 97 === Nanostructured materials can provide a large surface area for the loading of highly dispersed catalyst nanoparticles, such as Pt and Pt-Ru, thereby improving the power density of DMFCs. The thesis prepares various nanostructured anode electrocatalysts, and investigates electrocatalytic characteristics of the nanostructured catalysts.
Two different approaches are adopted to prepare electrocatalyst supports, which are anodic aluminum oxide (AAO) templated nanostructured materials and nanoporous graphitic carbon (g-C). For the AAO templation approach, Si nanocones (SNCs) and amorphous carbon (α-C) coated Si nanocones arrays are first fabricated on the Si wafer for the use as the catalyst support, followed by electrodeposition of Pt nanoparticles. Well-ordered α-C coated Si nanocone (ACNC) arrays were produced as a result of the arrangement pattern transfer of AAO pore channel arrays to Si substrates with TiOx nanomasks by the plasma etch in the microwave plasma chemical vapor deposition (MPCVD) system. A layer of α-C about 5 nm thick was in-situ deposited on the SNCs during the MPCVD process. In order to obtain the high current density and mass activity, well dispersed Pt nanoparticles with a uniform size distribution below 5 nm were deposited on ordered SNC and ACNC by bipolar pulse electrodeposition. The dispersion of Pt nanoparticles on SNC was improved by coating a nanocrystalline g-C. The electrocatalytic activity of the nanostructured anodes toward methanol oxidation reaction (MOR) are superior to anodes with a blanket surface according to electrochemical measurements.
In addition, we developed a new method to form nanoporous g-C, which was utilized as the support for Pt and Pt-Ru alloy catalysts, by the used of an adamantane flame. Electrochemical tests and results show the Pt-Ru supported on nanoporous g-C had excellent catalytic activity and stability toward methanol electrooxidation. The excellent catalytic activity may be attributed to the higher surface area of g-C.
To investigate the dependence of electrocatalytic activity toward MOR on the morphology of Pt catalyst, the two dimensional (2D) and three dimensional (3D) Pt nanostrucutred materials were also synthesized by direct bipolar pulse electrochemical deposition at 25○C. We have also successfully synthesized Pt nanoparticles of different shapes such as tetrahedron and cube by fasten silicon at room temperature. An electrochemical study of 2D, 3D and the shape-controlled Pt nanostructures were showing its potential application for efficient direct methanol fuel cells.
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