<br>银表面活性氧的结构和乙烯环氧化反应活性,ACS Catalysis

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银表面活性氧的结构和乙烯环氧化反应活性
ACS Catalysis ( IF 11.3 ) Pub Date : 2024-06-21 , DOI: 10.1021/acscatal.4c01566
Man Guo _{1,

2} , Nanchen Dongfang ₃ , Marcella Iannuzzi ₃ , Jeroen Anton van Bokhoven _{1,

2} , Luca Artiglia ₁

Affiliation

乙烯环氧化是最重要的工业催化反应之一，银基催化剂表现出优异的活性和选择性。反应过程中，氧在银表面被活化，并对产物选择性产生重大影响。值得注意的是，最顶层原子层中的氧物质极大地影响催化剂的反应活性。然而，它们在原位反应条件下的表征仍然是一个巨大的挑战，具体结构尚未确定。在这项研究中，我们采用原位 X 射线光电子能谱和密度泛函理论计算来确定银箔最顶层原子层形成的氧物种，并指定它们的结构。鉴定出银上活化的三组不同的氧物质：(i)表面晶格氧和源自缔合吸附分子氧的两种氧物质，以及(ii)顶部和(iii)表面下氧。进行瞬态原位光电子能谱实验以揭示乙烯环氧化反应环境下不同氧物种的动态演化和反应活性。来自吸附的相关双氧的顶部氧原子是最活跃的。同时，为处理时间分辨数据而开发的频率选择性数据分析方法可以深入了解不同氧物质的峰值强度的演变趋势。该方法的多功能性表明其在未来时间分辨表征研究中的潜在应用。

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Structure and Reactivity of Active Oxygen Species on Silver Surfaces for Ethylene Epoxidation

The epoxidation of ethylene stands as one of the most important industrial catalytic reactions, and silver-based catalysts show superior activity and selectivity. Oxygen is activated on the surface of silver during the reaction and exerts a substantial impact on product selectivity. Notably, the oxygen species residing in the topmost atomic layers profoundly influence the reactivity of a catalyst. However, their characterization under in situ reaction conditions remains a huge challenge, and specific structures have not been identified yet. In this study, we employ in situ X-ray photoelectron spectroscopy and density functional theory calculations to determine the oxygen species formed at the topmost atomic layers of a silver foil and to assign them a structure. Three different groups of oxygen species activated on silver are identified: (i) surface lattice oxygen and two oxygen species originating from associatively adsorbed dioxygen and (ii) top and (iii) subsurface oxygen. Transient in situ photoelectron spectroscopy experiments are carried out to reveal the dynamic evolution and thus reactivity of the different oxygen species under ethylene epoxidation reaction environments. The top oxygen atom from the adsorbed associated dioxygen is the most active. Meanwhile, a frequency-selective data analysis method, developed to process time-resolved data, provides insights into the evolving trends of peak intensities for different oxygen species. The versatility of this method suggests its potential application in future time-resolved characterization studies.

更新日期：2024-06-21

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