Institute of Surface Chemistry and Catalysis, Ulm University, 89081 Ulm, Germany.
Chemphyschem. 2010 May 17;11(7):1505-12. doi: 10.1002/cphc.201000105.
We report on the structural and electrochemical properties of Au(x)Pt(1-x) surface alloys prepared by Au vapour deposition onto Pt(111) followed by annealing to 1000 K. Driven by configurational entropy, Pt and Au atoms are distributed homogeneously over the surface. On the nm scale, however, atomically resolved scanning tunnelling microscopy images with chemical contrast reveal the formation of nm-sized Pt-rich and Au-rich aggregates, similar to the behaviour recently reported for Pd(x)Ru(1-x)/Ru(0001) [H. Hartmann, T. Diemant, A. Bergbreiter, J. Bansmann, H. E. Hoster, R. J. Behm, Surf. Sci. 2009, 603, 1439]. Based on the STM data, we determine the abundance of specific adsorption sites for different Au contents, and we derive effective pair interaction parameters that allow reproducing the lateral distribution in Monte Carlo simulations. Cyclic voltammograms of the surface alloys have many similarities with Pt(111). H(ad) and OH(ad) related features both decrease with increasing amount of Au. Both seem to adsorb only on Pt sites, but H(ad) requires smaller ensembles of Pt atoms than OH(ad). The onset potential for H(ad)-formation decreases with increasing Au content. This is can be explained by an effect of the Au atoms on the entropy of adsorption.
我们报告了通过在 Pt(111) 上沉积 Au 蒸气然后退火至 1000 K 制备的 Au(x)Pt(1-x)表面合金的结构和电化学性质。在构型熵的驱动下，Pt 和 Au 原子均匀分布在表面上。然而，在 nm 尺度上，具有化学对比度的原子分辨扫描隧道显微镜图像显示出形成 nm 大小的富 Pt 和富 Au 聚集体，类似于最近报道的 Pd(x)Ru(1-x)/Ru(0001) [H. Hartmann, T. Diemant, A. Bergbreiter, J. Bansmann, H. E. Hoster, R. J. Behm, Surf. Sci. 2009, 603, 1439] 的行为。基于 STM 数据，我们确定了不同 Au 含量下特定吸附位的丰度，并推导了有效对相互作用参数，这些参数允许在蒙特卡罗模拟中再现横向分布。表面合金的循环伏安曲线与 Pt(111) 有许多相似之处。H(ad)和 OH(ad)相关特征都随 Au 含量的增加而减少。两者似乎都只在 Pt 位上吸附，但 H(ad)需要比 OH(ad)更小的 Pt 原子集合。H(ad)形成的起始电位随 Au 含量的增加而降低。这可以用 Au 原子对吸附熵的影响来解释。
