Comparative Evaluation of Catalytic Counter Electrodes for Co(III)/(II) Electron Shuttles in Regenerative Photoelectrochemical Cells

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• 作者：Stefano Carli ; Eva Busatto ; Stefano Caramori ; Rita Boaretto ; Roberto Argazzi ; Cliff. J. Timpson ; Carlo Alberto Bignozzi
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：March 14, 2013
• 年：2013
• 卷：117
• 期：10
• 页码：5142-5153
• 全文大小：622K
• 年卷期：v.117,no.10(March 14, 2013)
• ISSN：1932-7455

文摘

Different PEDOT-based counter electrodes, obtained by potentiostatic electropolymerization of 3,4-ethylenedioxythiophene (EDOT) monomer on fluorine tin oxide (FTO) surfaces, were compared to platinum- and gold-coated electrodes in order to evaluate the potential use of PEDOT counter electrodes in dye-sensitized photoelectrochemical cells (DSCs). In particular, a series of DSC devices utilizing Co(III)/(II) polypyridine redox mediators ([Co(bpy)₃]^3+/2+, [Co(phen)₃]^3+/2+, [Co(dtb)₃]^3+/2+; bpy = 2,2鈥?bipyridine; dtb = 4,4鈥瞕itert-butyl-2,2鈥?bipyridine; phen = 1,10-phenanthroline) having distinct electrochemical characteristics were evaluated. Electrochemical impedance spectroscopy (EIS) measurements reveal that [Co(bpy)₃]^3+/2+ and [Co(phen)₃]^3+/2+ mediators exhibit relatively fast heterogeneous electron transfer rates with porous PEDOT/ClO₄ electrodes (k = 7 脳 10^鈥? cm s^鈥? and 2.1 脳 10^鈥? cm s^鈥?, respectively) and correspondingly low charge transfer resistances (<1 惟) that are competitive with results obtained for Au and Pt coated electrodes. The bulkier [Co(dtb)₃]^3+/2+ mediator exhibits a more complex surface dependent electrochemistry yielding somewhat faster electron transfer kinetics on gold (3.8 脳 10^鈥? cm s^鈥?) relative to PEDOT/ClO₄ (1.7 脳 10^鈥? cm s^鈥?) coated counter electrodes. Nevertheless, this work establishes that porous PEDOT/ClO₄ counter electrodes, because in part of their enhanced electroactive surface area and reduced charge transfer resistance, possess sufficient electrocatalytic properties when paired with cobalt-based redox mediators to make PEDOT-based counter electrodes attractive for use in DSC applications.