Shenyang National Laboratory for Materials Science (SYNL), Institute of Metal Research, Chinese Academy of Science, 72 Wenhua Rd., Shenyang 110016, China.
Nanoscale. 2017 Oct 12;9(39):15033-15043. doi: 10.1039/c7nr06018a.
Although nanosized Au clusters have been well developed for many applications, fundamental understanding of their adsorption/activation behaviors in catalytic applications is still lacking, especially when other elements provide promotion or hybridization functions. Au hybridized with Cu element is a highly investigated system; Cu is in the same element group as Au and thus displays similar physicochemical properties. However, their hybrids are not well understood in terms of their chemical states and adsorption/activation properties. In this work, typical γ-AlO-supported Au and CuO as well as Au-CuO nanoparticles were prepared and characterized to explore their adsorption/activation properties in depth using CO as a probe molecule using advanced techniques, such as XPS, HR-TEM, temperature programmed experiments and operando DRIFT combined with mass spectra. It was found that gold and copper can both act as active sites during CO adsorption and activation. The CO-TPD and operando DRIFT results also revealed that CO molecules were able to react with surface oxygenated species, resulting in the direct formation of CO over the three samples in the absence of gaseous O. The gold step sites (Au) participated more readily in the reaction, especially under gaseous O-free conditions. During adsorption, CO molecules were more preferentially adsorbed on Au sites at lower temperature comparing with those on the Cu sites. However, competitive adsorption occurred between CO adsorbed on Au and Cu with increased reaction temperature, and the synergy between the Au and Cu compositions was too strong to suppress the adsorption and activation of the CO molecules. The dynamic adsorption equilibrium over 120 °C to 200 °C resulted in the appearance of a hysteresis performance platform.
尽管纳米金簇在许多应用中得到了很好的发展，但对于它们在催化应用中的吸附/活化行为的基本理解仍然缺乏，特别是当其他元素提供促进或杂化功能时。金与铜元素的杂化是一个被广泛研究的体系；铜与金处于同一元素组，因此表现出相似的物理化学性质。然而，它们的混合物在化学状态和吸附/活化性质方面并没有得到很好的理解。在这项工作中，制备了典型的γ-Al2O3负载的 Au 和 CuO 以及 Au-CuO 纳米颗粒，并使用先进的技术（如 XPS、HR-TEM、程序升温实验和原位 DRIFT 结合质谱）对其进行了深入的研究，以 CO 作为探针分子来探索其吸附/活化性质。研究发现，金和铜在 CO 吸附和活化过程中都可以作为活性位。CO-TPD 和原位 DRIFT 结果还表明，CO 分子能够与表面氧化物种反应，导致在没有气态 O 的情况下，三种样品上直接形成 CO。金台阶位（Au）更容易参与反应，特别是在没有气态 O 的情况下。在吸附过程中，与 Cu 位相比，CO 分子在较低温度下更优先吸附在 Au 位上。然而，随着反应温度的升高，在 Au 和 Cu 位上吸附的 CO 之间发生了竞争吸附，Au 和 Cu 组成之间的协同作用太强，无法抑制 CO 分子的吸附和活化。在 120°C 至 200°C 的动态吸附平衡导致出现滞后性能平台。
