Comparative evaluation of catalytic counter electrodes for Co(III)/(II) electron shuttles in regenerative photoelectrochemical cells

Document Type

Article

Publication Title

Journal of Physical Chemistry C

Publication Date

3-14-2013

Abstract

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′-bipyridine; dtb = 4,4′ditert-butyl-2,2′-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/ClO 4 electrodes (k = 7 × 10-3 cm s-1 and 2.1 × 10-3 cm s-1, respectively) and correspondingly low charge transfer resistances (<1 Ω) 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 × 10-4 cm s-1) relative to PEDOT/ClO 4 (1.7 × 10-4 cm s-1) coated counter electrodes. Nevertheless, this work establishes that porous PEDOT/ClO 4 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. © 2013 American Chemical Society.

Volume

117

Issue

10

First Page

5142

Last Page

5153

DOI

10.1021/jp312066n

ISSN

19327447

E-ISSN

19327455

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