Electroreduction of Viologen Phenyl Diazonium Salts as a Strategy To Control Viologen Coverage on Electrodes

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• 作者：Liangcheng CaoGan Fang ; Yuechuan Wang
• 刊名：Langmuir
• 出版年：2017
• 出版时间：January 31, 2017
• 年：2017
• 卷：33
• 期：4
• 页码：980-987
• 全文大小：455K
• ISSN：1520-5827

文摘

A majority of the reported electrografting of aryldiazonium salts result in the formation of covalently attached films with a limited surface coverage of below 5 nmol·cm<sup>–2sup>. Herein, we report the preparation of higher-thickness redox-active viologen-grafted electrodes from the electroreduction of viologen phenyl diazonium salts, by either cyclic voltammetric (CV) sweeps or electrolysis using a fixed potential. Both of the methodologies were successfully applied for various conductive surfaces, including glassy carbon (GC), gold disc, indium tin oxide glass, mesoporous TiO<sub>2sub> electrodes, and 3D compacted carbon fibers. A robust maximal viologen coverage, Γ<sub>viologensub> = 9.5 nmol·cm<sup>–2sup>, was achieved on a GC electrode by CV electroreduction. Electroreduction held at a fixed potential at E<sub>appl.sub> = −0.3 V can fabricate viologen-grafted electrodes with Γ<sub>viologensub> in the range of 0–37 nmol·cm<sup>–2sup> in a controllable way, by simply adjusting the electrodeposition time t<sub>appl.sub>. Time-dependent Γ<sub>viologensub> were found to be 10 nmol·cm<sup>–2sup>@2 min, 20 nmol·cm<sup>–2sup>@4.2 min, and 30 nmol·cm<sup>–2sup>@7 min. Furthermore, a TiO<sub>2sub> electrode coupled with Γ<sub>viologensub> of 140 nmol·cm<sup>–2sup> exhibited electrochromic performance, with the color changing from pale yellow to blue and red brown.