title: Electroreduction of Viologen Phenyl Diazonium Salts as a Strategy To Control Viologen Coverage on Electrodes.
abstract: 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-2. 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 TiO2electrodes, and 3D compacted carbon fibers. A robust maximal viologen coverage, Γviologen= 9.5 nmol·cm-2, was achieved on a GC electrode by CV electroreduction. Electroreduction held at a fixed potential at Eappl.= -0.3 V can fabricate viologen-grafted electrodes with Γviologenin the range of 0-37 nmol·cm-2in a controllable way, by simply adjusting the electrodeposition time tappl.. Time-dependent Γviologenwere found to be 10 nmol·cm-2@2 min, 20 nmol·cm-2@4.2 min, and 30 nmol·cm-2@7 min. Furthermore, a TiO2electrode coupled with Γviologenof 140 nmol·cm-2exhibited electrochromic performance, with the color changing from pale yellow to blue and red brown.
authors.affiliation: Chongqing Institute of Green and Intelligent Technologies, Chinese Academy of Sciences , Fangzheng Avenue 266, Chongqing 400714, China.
authors.forename: Liangcheng
authors.identifier: 0000-0001-7970-7110
authors.initials: L
authors.lastname: Cao
authors.affiliation: Chongqing Institute of Green and Intelligent Technologies, Chinese Academy of Sciences , Fangzheng Avenue 266, Chongqing 400714, China.
authors.forename: Gan
authors.initials: G
authors.lastname: Fang
authors.affiliation: College of Polymer Science & Engineering, State Key Laboratory of Polymer Materials, Sichuan University , South Section of 1st Ring Road 24, Chengdu 610065, China.
authors.forename: Yuechuan
authors.identifier: 0000-0002-6753-0685
authors.initials: Y
authors.lastname: Wang