Enhancement of Ethanol Oxidation Reaction in Acidic Media of Pt Nanorods through Sn and Ag Alloying
| Autor: | Chao-Yu Yang, 楊詔宇 |
|---|---|
| Rok vydání: | 2016 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 104 In order to prepare Pt-based catalysts with high ethanol oxidation reaction (EOR) performance, binary and ternary nanorods (NRs) including PtAu, PtAg, PtSn, and PtSnAg with different degrees of oxophilicity is systematically elucidated. Besides, the effect of dealloying and one-dimentional (1-D) structures on the EOR performance of ternary PrSnAg NRs has been studied. The structures, surface compositions, chemical compositions, morphologies and electrochemical properties of prepared catalysts are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-atomic emission spectrometer (ICP-AES), high resolution transmission electron microscopy (HRTEM), and cyclic voltammetry (CV) technique, respectively. This study is divided into three parts. In the first part, the carbon-supported Pt-based binary and ternary NRs with an aspect ratio of about 2.7 are prepared via formic acid method. In EOR results, the current density of PtSnAg at 0.6 V is the highest, suggesting the surface oxides in PtSnAg can improve EOR activity by promotion of dissociative adsorption of ethanol on Pt surface and the CO oxidation reaction through bi-functional mechanism. Moreover, chronoamperometric (CA) results obtained at ambient temperature show that ternary PtSnAg catalyst have the highest current density and stability among all samples, attributed to the surface oxygen containing species (OCS) such as PtOx, and SnO2 and Ag alloying effect. In the second part, the dealloying process has been used to further improve the activity of the PtSnAg catalysts. After dealloying process of 5 cycles, the electrochemical surface area of PtSnAg can be enhanced about 3 folds, owing to Ag partial dissolution and the increase in the number of Pt active sites. Besides, the PtSnAg after dealloying of 10 cycles has the best EOR performance and durability, maybe attributed to the optimized surface Pt/Sn/Ag compositions. In the third part, the PtSnAg/C NRs with an aspect ratio of 7.2, 5.7, and 2.7 have been prepared at different temperatures (named as PtSnAg-5, PtSnAg-15 oC, and PtSnAg-RT, respectively). For the EOR performance of PtSnAg/C catalysts with different aspect ratios, the current density of PtSnAg-5 oC at 0.6 V is about 1.2 and 2.1 times higher than that of PtSnAg-15 oC and PtSnAg-RT. Besides, after CA test for 2 h, NRs prepared at 5 oC display the best durability, because the synergic effect of the higher aspect ratio and surface oxide can remove the COads and CHx. Compared the results in parts 2 and 3, it seems that morphologies control is more effective than the dealloying to promote the EOR performance of PtSnAg. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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