Two Sharp Phase Change Processes of Diphenyl Viologen at a Au(111) Electrode Surface: Non-Faradaic Transition with Interplay of Ionic Adsorption of Chloride and Bromide and Faradaic One
Two Sharp Phase Change Processes of Diphenyl Viologen at a Au(111) Electrode Surface: Non-Faradaic Transition with Interplay of Ionic Adsorption of Chloride and Bromide and Faradaic One
复制标题
二苯紫精在 Au(111) 电极表面的两个急剧相变过程：非法拉第转变与氯离子、溴离子吸附和法拉第一的相互作用
DOI：
10.1021/jp5099238
复制
发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Takamasa Sagara
中科院分区：
文献类型：
--
作者：
Tomohiro Higashi;Teppei Kawamoto;Soichiro Yoshimoto;Takamasa Sagara
利用伏安法、电反射（ER）和电化学扫描隧道显微镜（EC-STM）测量结果描述了二苯基紫精（dPhV）在KCl和KBr水溶液中Au（111）电极上的两个相变过程。两个过程都表现出尖锐的尖峰伏安响应。在KCl溶液中，0.30 V相对于Ag/AgCl/饱和KCl的相变被发现是非法拉第有序-无序相变，从具有比0.30 V更高正电势的共吸附Cl-的dPhV双阳离子（dPhV2+）的有序吸附层到正电势更低的气相。发现-0.09 V 时的法拉第反应是从气相到dPhV•+ 凝聚单层的转变。凝聚单层的 EC-STM 图像显示出 π-π 堆叠 dPhV•+ 行的条纹图案。在 KBr 溶液中观察到几乎相同的两个过程，但在 KF 溶液中则没有。在 KF 溶液中，虽然观察到两个伏安响应，但峰小而宽，表明单个 dPhV 阳离子的吸附状态变化缓慢。总而言之，共存阴离子的特异性吸附对于急剧的非法拉第相变的发生至关重要。
Two phase change processes of diphenyl viologen (dPhV) on a Au(111) electrode in KCl and KBr aqueous solutions were described using the results of voltammetric, electroreflectance (ER), and electrochemical scanning tunneling microscopic (EC-STM) measurements. Both processes exhibited sharp spikelike voltammetric responses. In KCl solution, the phase change at 0.30 V versus Ag/AgCl/saturated KCl was found to be a nonfaradaic order–disorder phase transition, from an ordered adlayer of dPhV dication (dPhV2+) with coadsorbed Cl–at more positive potentials than 0.30 V to a gaslike phase at less positive potentials. The faradaic reaction at −0.09 V was found to be the transition from the gaslike phase to a condensed monolayer of dPhV•+. The EC-STM images of the condensed monolayer showed stripe patterns of rows of π–π stacked dPhV•+. Almost the same set of two processes was observed in KBr solution but not in KF solution. In KF solution, although two voltammetric responses were observed, the peaks were small and broad, indicative of sluggish adsorption state changes of individual dPhV cations. Taken together, specific adsorption of coexistent anions is of critical importance for the occurrence of the sharp nonfaradaic phase transition.