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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Characterization and Reactivity of the Mo4S_6~+ Cluster Deposited on Au(111)
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Characterization and Reactivity of the Mo4S_6~+ Cluster Deposited on Au(111)

机译：Au（111）上沉积的Mo4S_6〜+团簇的表征和反应性

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Mass-selected cluster deposition was used to investigate the chemical and thermal properties of the Mo4S6 cluster deposited onto a Au(111) substrate. Auger spectroscopy and ~(13)CO thermal desorption measurements demonstrate that the clusters behave independently up to coverages of ～0.15 ML, while at higher coverages, cluster crowding or island formation results in no net increase in Mo-atom adsorption sites. DFT calculations show that CO binding on the Mo-atom top site is strongly preferred over the side sites, with scaled binding energies in reasonable agreement with the experimentally derived binding energy of 0.7 eV. DFT calculations predict that the total adsorption energy for sequential addition of two CO molecules (top and side site) is nearly additive, whereas the addition of a third CO to another empty Mo side site is less stable. The latter is attributed to repulsive intercluster interactions and is consistent with the experimentally estimated sticking coefficient of 0.4 ± 0.1. In contrast to CO, we were unable to detect any adsorption of NH3 onto the deposited cluster. The DFT calculations confirm these observations by predicting a very small NH3 adsorption energy to the Mo4S5/Au(1 11) supported cluster. The difference in adsorbate binding (CO, NH3) between the gas-phase and supported cluster highlights the role of the Au(111) substrate in modifying the electronic structure and chemical behavior of the supported cluster. Annealing of the Mo4S6/Au(111) surface above ～500 K was found to significantly reduce the CO uptake of the supported clusters. These data are consistent with diffusion of intact clusters along the Au surface and the formation of 2D islands. Because of the unique stoichiometry of the as-deposited Mo4S6 clusters, aggregates formed by cluster diffusion are expected to exhibit distinctly different chemical behavior compared to near-stoichiometric MoS_x (x≈ 2) platelet nanoclusters or amorphous thin films.
机译：质量选择的簇沉积用于研究沉积在Au（111）衬底上的Mo4S6簇的化学和热学性质。俄歇光谱和〜（13）CO热脱附测量结果表明，团簇的行为独立于〜0.15 ML的覆盖范围，而在更高的覆盖率下，簇拥挤或形成岛不会导致Mo原子吸附位点的净增加。 DFT计算表明，在Mo原子顶部位点上的CO结合力比在侧面位点上更受青睐，比例结合能与实验得出的0.7 eV的结合能合理吻合。 DFT计算预测，相继添加两个CO分子（顶部和侧面）的总吸附能几乎是相加的，而向另一个空Mo侧位添加第三种CO的稳定性较差。后者归因于排斥性簇间相互作用，并且与实验估计的粘附系数0.4±0.1一致。与CO相比，我们无法检测到NH3在沉积簇上的任何吸附。 DFT计算通过预测Mo4S5 / Au（1 11）支撑簇中很小的NH3吸附能来证实这些观察结果。气相和支撑簇之间吸附物结合（CO，NH3）的差异突出了Au（111）底物在修饰支撑簇的电子结构和化学行为方面的作用。发现Mo4S6 / Au（111）表面在〜500 K之上退火可以显着降低负载簇的CO吸收。这些数据与完整簇沿金表面的扩散以及二维岛的形成是一致的。由于沉积态的Mo4S6团簇具有独特的化学计量，与近化学计量的MoS_x（x≈2）血小板纳米团簇或非晶薄膜相比，通过团簇扩散形成的聚集体有望表现出截然不同的化学行为。

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