Novel view of the electrochemistry of gold

Burke, L.D.; Buckley, D. H.; Morrissey, Joanne

doi:10.1039/an9941900841

Cited by 61 publications

(40 citation statements)

References 21 publications

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“…40 The mechanism postulated for the oxidation of gold has been described elsewhere by Angerstein-Kozlowska et al 33 The oxidation process involves several steps. Initially, anions from the electrolyte are specifically adsorbed, but when the potential becomes large enough (pre-oxidation region) the hydroxide ions start to adsorb, desorbing the electrolyte anions in the process.…”

Section: Discussionmentioning

confidence: 99%

Structural changes during oxidation of Au(110)

Hale

Thurgate

Wilkie

2001

Surface & Interface Analysis

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The gold(110) single crystal exhibits a (1 × 2) surface structure when clean, but when immersed in 0.01 M HClO 4 under potential control the structure has been found to change. Throughout the double-layer region the structure remains as .1 × 2/ but when the potential is increased above 0.9-1.0 V vs. Ag/AgCl (the preoxidation region) the surface structure changes to a centred rectangular structure. This structure forms reproducibly but has limited stability. After the initial oxidation, the structure prevails until 1.2-1.3 V, whereupon oxidation occurs on a larger scale and the surface structure becomes .1 × 1/. These structures return to .1 × 2/ after reduction of the oxide, proving that the structural changes are reversible. X-ray photoelectron spectroscopy of these regions has shown a difference in the chemical state of the oxygen. Adsorbed perchlorate ion is initially the only oxygen component but as the potential increases the peak shifts into the hydroxide region and finally splits into a hydroxide peak and a metal oxide peak. This study indicates a new way of looking at the structure and composition of the gold surface and provides insight into the nature of the interaction between the surface and the solution.

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Section: Discussionmentioning

confidence: 99%

Structural changes during oxidation of Au(110)

Hale

Thurgate

Wilkie

2001

Surface & Interface Analysis

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“…Just a few cycles were recorded prior to voltammetric measurements to attain the reproducible shape of the curves. The upper limit of potential scan never exceeded 1.2 V (RHE) in order to prevent the anodic oxidation of gold underlayer [26,27]. The potential scan rate was 5 and 20 mV s À1 .…”

Section: Methodsmentioning

confidence: 99%

EQCM Study of Iridium Anodic Oxidation in H₂SO₄ and KOH Solutions

et al. 2005

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In the present study anodic oxidation of iridium layer formed thermally on a gold-sputtered quartz crystal electrode has been investigated by electrochemical quartz crystal microgravimetry (EQCM) in the solutions of 0.5 M H 2 SO 4 and 0.1 M KOH. The emphasis here has been put on the microgravimetric behavior of iridium as a metal, because a few previous EQCM studies reported in literature have been devoted to iridium oxide films (IROFs). The objective pursued here has been to elucidate the nature of the main voltammetric peaks, which occur at different ranges of potential in the solutions investigated. It has been found that anodic oxidation of iridium electrode in 0.5 M H 2 SO 4 and 0.1 M KOH solutions is accompanied by irregular fluctuations of the electrode mass at 0.4 V < E < 0.8 V followed by regular increase in mass at 0.8 V < E < 1.2 V. The cathodic process initially, at 1.2 V > E > 0.9 V, proceeds without any or with slight increase in electrode mass, whereas at E < 0.8 V a regular decrease in mass is observed. It has been found that mass to charge ratio characterizing the processes of interest is 2 to 3 g F À1 in acidic medium, whereas in the case of alkaline one it is 4 to 6 g F À1. The main pair of peaks seen in the voltammograms of Ir electrode in alkaline medium at E < 0.8 V is attributable to redox transition Ir(0) ! Ir(III), whereas those observed in the case of acidic medium at E > 0.8 V should be related to the redox process Ir(0) ! Ir(IV) going via intermediate stage of Ir(III) formation. As a consequence of these redox transitions, the gel-like surface layer consisting of Ir(III) or Ir(IV) hydrous oxides forms on the electrode surface.

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“…In the case of metal surfaces, it is established that solid metals can trap and store energy and exist in metastable or non-equilibrium superactivated states [24][25][26][27][28][29][30]. These active states may be generated via potential cycling, thermal treatment, abrasion or cathodisation, and metals such as Au, Pt, Cu, Ag and Pd may be readily superactivated [31][32][33][34][35]. While a clear understanding of the nature and especially the mode of operation of such sites is not available, the metastable states are generally assumed to involve lattice defects.…”

Section: Introductionmentioning

confidence: 99%

“…Since the metal atoms involved in such a reaction are of low lattice coordination number, on oxidation, they acquire a relatively large ligand coordination sphere to form an assembly of hydrated metal surfaquo clusters [31,32]. This process is associated with a number of anomalous redox characteristics: Oxidation of the metal surface at low potentials in the premonolayer region of a cyclic voltammogram is often observed, a phenomenon which is particularly well exemplified by Au, and super-Nernstian shifts in redox potential with changes in solution pH, arising from the anionic nature of the incipient hydrous oxides [24][25][26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

The mechanism of oxygen evolution at superactivated gold electrodes in aqueous alkaline solution

Doyle¹,

Lyons²

2014

J Solid State Electrochem

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The cathodic superactivation of gold using a repetitive potential cycling procedure is reported, and its significance for the oxygen evolution reaction is discussed. The superactivated surfaces exhibit a transient oxygen evolution response subsequent to monolayer oxidation and prior to extensive visible oxygen evolution. The kinetics of this oxygen evolution process are studied using a variety of transient and steady-state electrochemical techniques. The Tafel slope is shown to decrease with increased activation of the gold surface from ca. 120 to ca. 48 mV dec −1 , and the charge transfer kinetics are enhanced by over three orders of magnitude for the superactivated electrodes. A mechanistic scheme involving the formation of monomeric Au(III) hydroxyl complexes of the form Au(OH) 6 3− is proposed. The latter are of a transient nature and may be regarded as intermediates in the early stages of hydrous ß-oxide growth. These labile species may catalyse oxygen evolution by enhancing the formation of peroxy species that subsequently decompose with loss of oxygen gas from the surface oxide. This novel mechanistic route is in excellent agreement with recent literature studies and has the potential to unite a number of strands in the current understanding of the oxygen evolution reaction at gold surfaces.

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Novel view of the electrochemistry of gold

Cited by 61 publications

References 21 publications

Structural changes during oxidation of Au(110)

Structural changes during oxidation of Au(110)

EQCM Study of Iridium Anodic Oxidation in H₂SO₄ and KOH Solutions

The mechanism of oxygen evolution at superactivated gold electrodes in aqueous alkaline solution

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Novel view of the electrochemistry of gold

Cited by 61 publications

References 21 publications

Structural changes during oxidation of Au(110)

Structural changes during oxidation of Au(110)

EQCM Study of Iridium Anodic Oxidation in H2SO4 and KOH Solutions

The mechanism of oxygen evolution at superactivated gold electrodes in aqueous alkaline solution

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EQCM Study of Iridium Anodic Oxidation in H₂SO₄ and KOH Solutions