Insight into the nature of transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions is obtainable from a number of surface spectroscopic techniques. Carrying out these investigations under actual reaction conditions is preferred but remains challenging, especially for catalytic reactions that occur in water. Here, we report the direct spectroscopic study of the catalytic hydrodechlorination of 1,1-dichloroethene in H2O using surface-enhanced Raman spectroscopy (SERS). With Pd islands grown on Au nanoshell films, this reaction can be followed in situ using SERS, exploiting the high enhancements and large active area of Au nanoshell SERS substrates, the transparency of Raman spectroscopy to aqueous solvents, and the catalytic activity enhancement of Pd by the underlying Au metal. The formation and subsequent transformation of several adsorbate species was observed. These results provide the first direct evidence of the room-temperature catalytic hydrodechlorination of a chlorinated solvent, a potentially important pathway for groundwater cleanup, as a sequence of dechlorination and hydrogenation steps. More broadly, the results highlight the exciting prospects of studying catalytic processes in water in situ, like those involved in biomass conversion and proton-exchange membrane fuel cells.

中文翻译：

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使用表面增强拉曼光谱在 Pd-Au 纳米壳上原位观察金属催化的化学反应

通过多种表面光谱技术可以深入了解瞬态反应中间体的性质和非均相催化化学反应中涉及的机械途径。在实际反应条件下进行这些研究是首选，但仍然具有挑战性，特别是对于发生在水中的催化反应。在这里，我们报告了使用表面增强拉曼光谱 (SERS) 对 H2O 中 1,1-二氯乙烯催化加氢脱氯的直接光谱研究。通过在 Au 纳米壳膜上生长 Pd 岛，可以使用 SERS 原位跟踪该反应，利用 Au 纳米壳 SERS 基底的高增强和大活性面积、拉曼光谱对水性溶剂的透明度以及 Pd 的催化活性增强底层金金属。观察到几种吸附物种类的形成和随后的转化。这些结果为氯化溶剂的室温催化加氢脱氯提供了第一个直接证据，这是净化地下水的潜在重要途径，作为一系列脱氯和加氢步骤。更广泛地说，这些结果突出了原位研究水中催化过程的令人兴奋的前景，例如涉及生物质转化和质子交换膜燃料电池的那些过程。