Hydrogenation of Cinnamaldehyde on Cu(110) Single-Crystal Surfaces
Hydrogenation of Cinnamaldehyde on Cu(110) Single-Crystal Surfaces
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DOI：
10.1021/acs.jpcc.1c04474
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发表时间：
2021-07
期刊：
影响因子：
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通讯作者：
Bo Chen;F. Zaera
中科院分区：
文献类型：
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作者：
Bo Chen;F. Zaera
采用程序升温脱附实验(TPD)和等温程序升温脱附实验(IsoTPD)研究了肉桂醛和氢在铜(110)单晶表面的化学反应。研究发现，氢化反应只有在使用原子氢的情况下才能发生，因为氢气与氢气的反应是不可检测的，而且氢化反应选择性地发生在羰基部分，以生成所需的肉桂醇。这种分子占所有产品的三分之二以上，其余的对应于更广泛的氢化肉桂醇。有趣的是，通过C-═-C键的氢化生成氢化肉桂醛(不受欢迎的产物)的过程可以忽略不计。在清洁和氧处理的表面上也观察到了相同的化学成分，这表明铜原子的氧化状态可能不是决定这种转化选择性的重要因素。此外，两种类型的实验，TPD和IsoTPD，都导致了相同的结果，观察到两个吸附物种(不饱和醛和原子氢)之间的朗缪尔-辛谢尔伍德机制。这些结果在分子水平上证实了单原子合金催化剂中铜表面的本征加氢选择性。
Temperature-programmed desorption experiments in two modalities, namely, using linear temperature ramping (TPD) and under isothermal conditions (IsoTPD), were performed to characterize the chemical reaction between cinnamaldehyde and hydrogen on Cu(110) single-crystal surfaces. It was found that hydrogenation can only take place if atomic hydrogen is used, as reactivity with H2was not detectable, and that it occurs selectively at the carbonyl moiety to produce the cinnamyl alcohol, the desired product. That molecule accounts for more than two-thirds of all the products, with the rest corresponding to the more extensively hydrogenated hydrocinnamyl alcohol. Interestingly, the production of hydrocinnamaldehyde (the undesired product) via the hydrogenation of the C═C bond is negligible. The same chemistry was observed on clean and oxygen-pretreated surfaces, indicating that the oxidation state of the Cu atoms may not be significant in determining selectivity for this conversion. Also, both types of experiments, TPD and IsoTPD, led to the same results, an observation that points to a Langmuir–Hinshelwood mechanism between two adsorbed species (the unsaturated aldehyde and atomic hydrogen). These results provide molecular-level confirmation of the intrinsic hydrogenation selectivity of Cu surfaces in single-atom alloy catalysts.