Density functional theory study of ethanol decomposition reaction over Ni/α-Al2O3(0001) surface
| Autor: | Ya-chin Cheng, 程雅琴 |
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| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 Ethanol decomposition on clean α-Al2O3 (0001) and Ni/α-Al2O3 (0001) surface was studied using periodic DFT calculations. Our results are compared with the available experimental findings of ethanol steam reforming reaction. For n Ni atoms (n=3–4) deposition on α-Al2O3(0001) surface, the preferential structure is forming cluster rather than dispersion on surface. Triangle Ni3 cluster adsorption on 2 × 2 α-Al2O3(0001) surface is used to represent Ni/α-Al2O3(0001) surface. The considered possible pathways for ethanol decomposition on clean α-Al2O3 (0001) and Ni/α-Al2O3 (0001) surface include dehydrogenation and C－C bond cleavage. Clean α-Al2O3 (0001) surface favors the reaction of ethanol dehydration to ethylene or leading to stable intermediate (CH2CHO) which finally occupies the active site of surface. Ni/α-Al2O3 (0001) surface shows high activity to inhibit coke formation, one feasible channel leading to C－C bond breaking was proposed. The C－C bond in CH2CO intermediate can be weaken via transforming the adsorption structure to increase the coordination number of the two carbon atoms with the surface of Ni cluster. The CH2CH2O(a) → CH2CHO (a) + H(a) reaction is the rate-determining step for the overall reaction (‡E = 1.20 eV). CO oxidation on Ni/α-Al2O3 (0001) surface is also investigated and the DOS analysis for CO adsorption on Ni bridge site shows that the interaction is mainly contributed from CO(5σ)－Ni charge donation and Ni(d)－2π* backdonation. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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