Nakamura Masashi, Banzai Takahiro, Maehata Yuto, Endo Osamu, Tajiri Hiroo, Sakata Osami, Hoshi Nagahiro
Department Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba, 263-8522, Japan.
Department of Organic and Polymer Materials Chemistry, Faculty of Engineering, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Koganei, Tokyo, 184-8588, Japan.
Sci Rep. 2017 Apr 20;7(1):914. doi: 10.1038/s41598-017-01048-0.
Understanding the electrocrystallization mechanisms of metal cations is of importance for many industrial and scientific fields. We have determined the transitional structures during underpotential deposition (upd) of various metal cations on Au(111) electrode using time-resolved surface X-ray diffraction and step-scan IR spectroscopy. At the initial stage of upd, a characteristic intensity transient appears in the time-resolved crystal truncation rod depending on metal cations. Metal cations with relatively high coordination energies of hydration water are deposited in two steps: first, the hydrated metal cations approached the surface and are metastably located at the outer Helmholtz plane, then they are deposited via the destruction of the hydration shell. However, Tl and Ag, which have low hydration energy, are rapidly adsorbed on Au(111) electrode without any metastable states of dehydration. Therefore, the deposition rate is strongly related to the coordination energy of the hydration water. Metal cations strongly interacting with the counter coadsorbed anions such as Cu in sulfuric acid causes the deposition rate to be slower because of the formation of complexes.
了解金属阳离子的电结晶机制在许多工业和科学领域都很重要。我们使用时间分辨表面X射线衍射和步进扫描红外光谱法确定了各种金属阳离子在Au(111)电极上欠电位沉积（upd）过程中的过渡结构。在upd的初始阶段，根据金属阳离子的不同，时间分辨晶体截断棒中会出现特征性的强度瞬变。水合水配位能相对较高的金属阳离子分两步沉积：首先，水合金属阳离子靠近表面并亚稳地位于外亥姆霍兹平面，然后通过水合壳层的破坏进行沉积。然而，水合能较低的Tl和Ag会迅速吸附在Au(111)电极上，不存在任何脱水的亚稳态。因此，沉积速率与水合水的配位能密切相关。在硫酸中，与共吸附的抗衡阴离子强烈相互作用的金属阳离子（如Cu），由于形成络合物，导致沉积速率较慢。
