Au(111)上Pd电沉积初始阶段ECSTM——PdSO_4溶液研究

应用电化学扫描隧道显微镜(ECSTM)研究了PdSO4溶液中Au(111)电极表面Pd的电化学沉积过程.实验表明,Pd的沉积初始阶段在Au(111)电极表面依次生成两个满单层Pd膜,这一实验结果不仅与电位扫描一致,而且更进一步地证明了起初的两个Pd单层形成过程乃以层～层外延方式生长.高分辨的原子图像表明吸附的SO2-4离子在外延生长的Pd膜表面形成了有序的(3×7)R19°结构.

Initial Stages of Pd Deposition onto Au(111) Electrodes from PdSO4 Solution

Metal thin films have attracted considerable interest in relation to catalysis, energy, material, corrosion and environmental protection. Pd thin film is capable of proton reduction and strong hydrogen absorption, which has shown electrocatalytic activity to the oxidation of small organic molecules. In this paper, in_situ STM measurements are performed to study the deposition process and the influence of the surface structure and anion adsorption. When Pd is deposited from PdSO4 solution on Au(111) in the UPD range, a monolayer of Pd with pseudomorphic (1×1) structure was formed on the substrate with induced (3×7) R19° SO2-4 adsorption. With decreasing potential the OPD range, the second pseudomorphic monolayer is formed with induced SO2-4 adsorption similar to that on the first monolayer. When the Pd reaches more than two monolayers, the deposition process changes to follow three_dimensional growth model with increased defects. Pd deposition from PdSO4 on Au (111) (1×1) follows the epitaxial way to form two complete monolayers of Pd film, in which induced anion adsorption on Pd film could play an important role.