乙醇氧化反應於鉑合金(111)表面上之理論計算研究

Computational study of ethanol oxidation reaction (EOR) on Pt-based Alloys

呂雯華(LU WEN-HUA)

指導教授 ： 王禎翰

國立臺灣師範大學/理學院/化學系/碩士(2016年)

https://doi.org/10.6345/NTNU202204493

摘要

本篇計算論文為乙醇氧化反應於Pt-合金(111)表面上的相關探究。本次利用計算乙醇氧化至乙醛之兩電子轉移的活化能障大小，來探究各合金催化表面的反應活性，其中研究的表面包含二元及三元合金(Pt3Sn、 Pt3Ru、 Pt3Rh、 Pt3Ag、 Pt3Au、 Pt3Pd和Pt6SnAg)；從計算的結果中可得出，當添加金屬Sn、Ru或同時添加Sn及Ag來取代部分金屬Pt時，相較於純金屬Pt催化表面，可以提升其反應活性，推估是因為添加這些金屬做取代時，能增加CH3CH2O*的吸附能，藉此幫助O-H斷鍵以增加其反應活性；除此之外，本次也藉由分析EOR相關吸附物及乾淨表面的segregation energy來探討其穩定度，綜合這些結果，認為三元合金PtAgSn對乙醇氧化反應有較高的活性及穩定度，最後我們也藉由計算CO於表面上的吸附能及氧化反應來探究於乙醇氧化反應中CO 毒化對各合金表面的影響，從計算結果中，可得出一結論，即是金屬Sn或Ag的添加可以弱化CO的吸附及降低其氧化能障，藉此移除表面的CO，以達到抑制CO毒化的現象

關鍵字

密度泛函理論 ； 乙醇氧化反應 ； CO 毒化 ； 鉑合金

並列摘要

This thesis computationally studied the ethanol oxidation reaction (EOR) on Pt-based alloys, including Pt6SnAg, Pt3Sn, Pt3Ru, Pt3Rh, Pt3Ag, Pt3Au and Pt3Pd. The EOR activity has been estimated by computing the reaction barriers for ethanol transferring to acetaldehyde in the 2-electron oxidation reaction. The energetic result shows that dopants of Sn,Ru or both Sn and Ag can better improve the activity than pure Pt electrode, attributable to their enhanced adsorption energy for CH3CH2O* intermediates. Additionally, EOR stability has been examined by analyzing the segregation energy of the clean and EOR intermediate (CH3CH2O*/CH3CHOH*) adsorbed alloys to simulate the as-prepared and under EOR operating electrodes. The analysis finds that both Sn and Ag doped Pt alloys have better stability and survived under EOR operation. Finally, we investigated CO poisoning in EOR by computing the energies for CO adsorption and oxidation on those alloys. The energetic results indicate that Sn and Ag doped alloys have rather weaker adsorption energy and low oxidation barriers for CO; thus, can better resist for its poisoning effect.

並列關鍵字

density function theory ； ethanol oxidation reaction ； CO-poisoning ； Pt-Alloy

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