Reaction of Au(111) with sulfur and oxygen: Scanning tunneling microscopic study
Reaction of Au(111) with sulfur and oxygen: Scanning tunneling microscopic study
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DOI：
10.1007/s11244-005-7864-4
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发表时间：
2005-08-01
影响因子：
3.6
通讯作者：
Friend, CM
中科院分区：
文献类型：
--
作者：
Min, BK;Alemozafar, AR;Friend, CM
硫和氧与金表面的反应在许多技术应用中都很重要，包括非均相催化、腐蚀和化学传感器。为了更好地了解Au（111）的表面结构和催化活性的来源，我们利用扫描隧道显微镜（STM）研究了Au（111）上的反应。我们发现Au（111）表面在硫和氧的沉积过程中动态重构，这些结构的变化促进了Au对SO2和O-2解离的反应性。具体来说，当S或O沉积在表面时，Au（111）人字形重建会上升。我们将这种结构变化归因于这些电负性吸附物通过电荷重新分配降低了拉伸表面应力。这种重建的提升伴随着金原子从人字结构中释放出来。在高覆盖范围内，通过从表面的规则阶地位置提取金原子，形成金硫化物或金氧化物簇。伴随重组的是金原子从人字结构中释放出来，形成锯齿状阶梯边缘或小金岛，从而产生密度更高的低配位金位点。这些欠配位的金原子可能在氧解离或SO2分解等反应中对金的催化活性的增强起重要作用。我们的研究结果进一步阐明了硫、氧和Au（111）表面之间的相互作用，并表明Au纳米团簇在可还原金属氧化物上的反应性可能与Au从这些小岛屿的边缘容易释放有关。我们的研究结果揭示了导致Au纳米团簇失活的烧结机制，以及在Au上使用硫醇基自组装单层（sam）的软光刻中边缘清晰度的基本限制。此外，从表面释放欠配位原子后，Au的反应性增强，表明氧化物载体对高反应性的作用相对较小。
The reaction of sulfur and oxygen with the gold surface is important in many technological applications, including heterogeneous catalysis, corrosion, and chemical sensors. We have studied reactions on Au(111) using scanning tunneling microscopy (STM) in order to better understand the surface structure and the origin of gold's catalytic activity. We find that the Au(111) surface dynamically restructures during deposition of sulfur and oxygen and that these changes in structure promote the reactivity of Au with respect to SO2 and O-2 dissociation. Specifically, the Au(111) herringbone reconstruction lifts when either S or O is deposited on the surface. We attribute this structural change to the reduction of tensile surface stress via charge redistribution by these electronegative adsorbates. This lifting of the reconstruction was accompanied by the release of gold atoms from the herringbone structure. At high coverage, clusters of gold sulfides or gold oxides form by abstraction of gold atoms from regular terrace sites of the surface. Concomitant with the restructuring is the release of gold atoms from the herringbone structure to produce a higher density of low-coordinated Au sites by forming serrated step edges or small gold islands. These undercoordinated Au atoms may play an essential role in the enhancement of catalytic activity of gold in reactions such as oxygen dissociation or SO2 decomposition. Our results further elucidate the interaction between sulfur and oxygen and the Au(111) surface and indicate that the reactivity of Au nanoclusters on reducible metal oxides is probably related to the facile release of Au from the edges of these small islands. Our results provide insight into the sintering mechanism which leads to deactivation of Au nanoclusters and into the fundamental limitation in the edge definition in soft lithography using thiol-based self-assembled monolayers (SAMs) on Au. Furthermore, the enhanced reactivity of Au after release of undercoordinated atoms from the surface indicate a relatively insignificant role of an oxide support for high reactivity.