Silver-Based Nanocubes as Catalysts for Electroless Copper Deposition and Oxygen Reduction Reaction
| Autor: | Yao-Lung Tsai, 蔡曜隆 |
|---|---|
| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 (1) Specific and mass activity of silver nanocube and nanoparticle-based catalyst for electroless copper deposition Catalytic activity normalized with respect to mass and electrochemical surface areas (ESA) are used herein to estimate the mass activity and specific activity, respectively, of Ag nanomaterials for catalysing electroless copper deposition (ECD). The activities and resulting acerage deposition rates were compared for Ag nanocubes enclosed by (100) planes and Ag nanoparticles. On the basis of mass evaluation and deposition kinetics measured using a quartz crystal microbalance (QCM), the mean mass activities of nanocubes and nanoparicles are determined to be 1.228 and 1.923, respectively. The Ag nanocubes show weaker mass activity and smaller ESA than do Ag nanoparticles. The resulting average deposition rates in terms of mass activity are 3.5×10-3 s-1 and 5.5×10-3 s-1 for nanocubes and nanoparticles, respectively. In contrast, a careful comparison of specific activity demonstrates that the Ag nanocubes show a better activity (5.4×10-2 mg cm-2) than do Ag nanoparticles (4×10-2 mg cm-2). The average deposition rates in terms of specific activity are 1.54×10-4 mg cm-2 s-1 and 1.16×10-4 mg cm-2 s-1 for nanocubes and nanoparticles, respectively；thus, nanocubes enable faster ECD. Similarly, in the Tafel plot normalised to the ESA, the specific current density corresponding to nanocubes were found to be higher than that in the case of nanoparticles for formaldehyde oxidation. The QCM and Tafel results demonstrate that the (100) planes in Ag nanocubes can enhance the catalytic activity of the nanocubes in ECD. (2) Performance of silver nanocubes based on electrochemical surface area for catalyzing oxygen reduction reaction Ag nanocubes that are 45 nm in size are synthesized and successfully used as catalysts in oxygen electroreduction. Electrochemical surface areas (ESAs) are considered to determine the effect on HO2- production, which is found to be in the following order: nanocubes＜ nanoparticles. Comparative data generated using Tafel analyses in 0.1 M NaOH electrolyte without and with methanol show that unchanged slopes on the prepared cubic catalysts can indicate high resistance of Ag nanocubes for methanol oxidation during oxygen reduction reaction. Compared with Ag catalysts, nanocubes exhibit 9.29×10-2 mA cm-2 (at -0.15 V vs. Ag/AgCl), the better activity in the oxygen reduction reaction. (3) Core-shell-shell Ag-Pt-Ag nanocubes：electrochemical dealloying for determination structure and catalysis on oxygen reduction reaction A successful determination on core-shell-shell structures of Ag-Pt-Ag nanocubes by using dealloying process is studied. As a result supported by electrochemical quartz crystal microbalance, the deallying process for Ag-Pt-Ag nanocubes is completed and hollow Ag-Pt/core-shell nanocubes are obtained after the third cycle using cyclic voltammetric method in 0.5 M H2SO4 electrolyte. Comparative data generated using cyclic voltammetric analyses in 0.1 M NaOH electrolyte show that the hollow nanocubes with Ag-Pt/core-shell structures can show a slack curve of 50 mVs-1 and significant peaks of 200 mVs-1 for hydrogen adsorption/evolution, respectively. Additionally, the Ag-Pt-Ag nanocubes and hollow Ag-Pt nanocube are used as catalysts for oxygen reducetion reaction. In comparison, the hollow catalysts show higher activity and faster kinetics. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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