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Issue 13, 2009
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Redox switching and oxygen evolution electrocatalysis in polymeric iron oxyhydroxide films

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Abstract

Outstanding issues regarding the redox switching characteristics and the oxygen evolution reaction (OER) electrocatalytic behaviour of multicycled iron oxyhydroxide films in aqueous alkaline solution have been examined. Charge percolation through the hydrous layer has been quantified, using cyclic voltammetry, in terms of a charge transport diffusion coefficient DCT which admits a value of ca. 3 × 10−10 cm2 s−1. Steady-state Tafel plot analysis and electrochemical impedance spectroscopy have been used to elucidate the kinetics and mechanism of oxygen evolution. Tafel slope values of ca. 60 mV dec−1 and ca. 120 mV dec−1 are found at low and high overpotentials respectively, whereas the reaction order with respect to hydroxide ion activity changes from ca. 3/2 to ca. 1 as the potential is increased. These observations are rationalised in terms of a kinetic scheme involving Temkin adsorption and the rate determining formation of a physisorbed hydrogen peroxide intermediate on the oxide surface. The dual Tafel slope behaviour is ascribed to the potential dependence of the surface coverage of adsorbed intermediates.

Graphical abstract: Redox switching and oxygen evolution electrocatalysis in polymeric iron oxyhydroxide films

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Article information


Submitted
02 Sep 2008
Accepted
18 Dec 2008
First published
06 Feb 2009

Phys. Chem. Chem. Phys., 2009,11, 2203-2217
Article type
Paper

Redox switching and oxygen evolution electrocatalysis in polymeric iron oxyhydroxide films

M. E. G. Lyons and M. P. Brandon, Phys. Chem. Chem. Phys., 2009, 11, 2203
DOI: 10.1039/B815338H

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