Polyaniline-Supported Atomic Gold Electrodes: Comparison with Macro Electrodes
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Polyaniline-Supported Atomic Gold Electrodes: Comparison with Macro Electrodes Ilana Schwartz • Alex P. Jonke • Mira Josowicz Jirˇ´ı Janata
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Received: 16 July 2012 / Accepted: 16 August 2012 / Published online: 11 September 2012 Ó Springer Science+Business Media, LLC 2012
Abstract Under precisely controlled conditions, atomic gold electrodes with even or odd number of Au atoms per polyaniline repeat unit (Pt/PANI/AuN for 0 \ N \ 7) were prepared. The electrochemical behavior of these new electrodes is compared with that of macro gold and PANI coated platinum electrodes by testing electrochemical oxidation of n-propanol and iso-propanol. This study allowed us to separate the behavior dominated by that of macroscopic gold in strongly alkaline medium and by that of the quantized odd–even effect of atomic gold. Within this overarching scope, there is a specific oxidation pattern attributable to the structural differences between the two isomers of propanol. The significance of this research lies in the recognition of high specific catalytic activity of atomic gold, which is at least three orders of magnitude higher than that of bulk gold for the oxidation of alcohols. It points to a substantial saving of the precious metal without the loss of catalytic activity, which is important in fuel cells and in other energy conversion device applications. Keywords Atomic metals Odd–even pattern Propanol electrooxidation Gold electrodes
Electronic supplementary material The online version of this article (doi:10.1007/s10562-012-0895-0) contains supplementary material, which is available to authorized users. I. Schwartz A. P. Jonke M. Josowicz J. Janata (&) School of Chemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA e-mail: [email protected]
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1 Introduction Interest in the electro catalytic oxidation of alcohols has increased greatly due to their potential application in fuel cells [1–3]. This oxidation can be catalyzed by a variety of metals, two of the most active being platinum and gold [3–7]. These metals can either be used in polycrystalline form or as large, polydispersed cluster aggregates containing millions of metal atoms. The aim of this paper is to compare electrochemical behavior of polycrystalline gold electrodes, polycrystalline platinum electrodes, and Pt electrodes coated with polyaniline containing defined atomic Au particles (Pt/PANI/AuN with N = 2–7). The electrochemistry of electrodes with N = 1 was indistinguishable from that of N = 0. Polyaniline polymerized from an acidic medium has been used as a support matrix for the insertion of metal clusters [8, 9]. It is a stable conjugated polymer, which is unique due to its ionic and electronic conductivity [10, 11]. Electro polymerization of aniline is done typically in acidic medium and results in the protonated emeraldine (semiquinone) form of PANI. The protonated imine functionality of the PANI has a strong affinity for certain complexed metal anions. In this paper we utilized the strong complexation of Au
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