Borissov D, Aravinda C L, Freyland W
University of Karlsruhe, Institute of Physical Chemistry, Kaiserstrasse 12, 76128 Karlsruhe, Germany.
J Phys Chem B. 2005 Jun 16;109(23):11606-15. doi: 10.1021/jp0443106.
Underpotential deposition (UPD) of Ag on Au(111) has been studied with two different electrolytes: aqueous 0.1 M H2SO4 solution in comparison with the ionic liquid 1-butyl-3-methylimidazolium chloride BMICl + AlCl3. Of particular interest is the distinct behavior of 2D phase formation at both interfaces, which has been investigated by cyclic and linear sweep voltammetry in combination with in situ electrochemical scanning tunneling microscopy (STM). It is found that one monolayer (ML) of Ag is formed in the UPD region in both electrolytes. In aqueous solution, atomically resolved STM images at 500 mV versus Ag/Ag+ show a (3 x 3) adlayer of Ag, whereas after sweeping the potential just before the commencement of the bulk Ag deposition, a transition from expanded (3 x 3) to pseudomorphic ML of Ag on Au(111) occurs. In BMICl-AlCl3, the first UPD process of Ag exhibits two peaks at 410 and 230 mV indicating that two distinct processes on the surface take place. For the first time, STM images with atomic resolution reveal a transition from an inhomogeneous to an ordered phase with a (square root of 3 x square root of 3)R30 degrees structure and an adsorption of AlCl4- anions having a superlattice of (1.65 x square root of 3)R30 degrees preceding the deposition of Ag.
已使用两种不同的电解质研究了银在金（111）上的欠电位沉积（UPD）：与离子液体1-丁基-3-甲基咪唑氯化物BMICl + AlCl3相比的0.1 M硫酸水溶液。特别令人感兴趣的是两个界面处二维相形成的独特行为，已通过循环和线性扫描伏安法结合原位电化学扫描隧道显微镜（STM）对其进行了研究。发现在两种电解质的UPD区域中均形成了单层（ML）的银。在水溶液中，相对于Ag/Ag+在500 mV下的原子分辨STM图像显示出银的（3×3）吸附层，而在刚好在大量银沉积开始之前扫描电位之后，在金（111）上发生了从扩展的（3×3）到银的赝晶ML的转变。在BMICl-AlCl3中，银的第一个UPD过程在410和230 mV处出现两个峰，表明表面发生了两个不同的过程。首次，具有原子分辨率的STM图像揭示了从非均匀相到具有（√3×√3）R30°结构的有序相的转变，以及在银沉积之前具有（1.65×√3）R30°超晶格的AlCl4-阴离子的吸附。
