A near ambient pressure XPS study of Au oxidation

Klyushin, Alexander Yu.; Rocha, Túlio C. R.; Hävecker, Michael; Knop‐Gericke, Axel; Schlögl, Robert

doi:10.1039/c4cp00308j

Cited by 140 publications

(104 citation statements)

References 43 publications

(58 reference statements)

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“…Phoptoelectron line Au 4f 7/2 is also fitted to two components: one at (84.4 eV), and the shoulder at 83.9 eV, corresponding to bulk Au(111) and to restuctured surface atoms, respectively, are also slightly shifted compared to literature data, 47 most likely due to the previous exposure of the electrode to the ambient conditions. 48 Is/Ib ratio is 0.23, and their separation is 0.5 eV, slightly higher than reported earlier, 47 most likely due to the higher roughness of the initial Au(111), prepared electrochemically. 48 With the addition of Rh overlayer, Fig.…”

Section: Resultscontrasting

confidence: 56%

“…48 Is/Ib ratio is 0.23, and their separation is 0.5 eV, slightly higher than reported earlier, 47 most likely due to the higher roughness of the initial Au(111), prepared electrochemically. 48 With the addition of Rh overlayer, Fig. 6b, the first component of Au 4f 5/2 line remains unchanged, while the second one is shifted to 86.5 eV.…”

Section: Resultscontrasting

confidence: 56%

“…The shift of the surface component for 0.3 eV indicate its interaction with the deposited Rh islands. For Au 4f 7/2 lines, tha ratio Is/Ib is 0.47, indicating the increased fraction of surface component than in the case of clean Au(111), while the separation of two components is 0.67 eV, also higher than for clean Au(111), both due to the increased roughness 48 of Rh/Au(111) surface. Electroactive surface area of Rh/Au(111) was calculated from CO stripping curves, which are presented in the same Fig.…”

Section: Resultsmentioning

confidence: 88%

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Spontaneously Deposited Rh on Au(111) Observed by AFM and XPS: Electrocatalysis of Hydrogen Evolution

Štrbac

Smiljanić

Rakočević

2016

J. Electrochem. Soc.

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Rhodium nanoislands were spontaneously deposited on Au(111) up to a full coverage. Obtained Rh/Au(111) bimetallic surface was characterized ex situ by Atomic Force Microscopy imaging and by X-Ray Photoelectron Microscopy, while in situ characterization was performed by Cyclic Voltammetry in 0.1 M NaOH solution. Pronounced catalysis of hydrogen evolution reaction has been observed on Rh modified Au(111) surface compared to bare Au(111). This is ascribed to the suitable geometry of obtained Rh/Au(111) nanostructured electrode surface providing large number of active sites and to the electronic interaction between Au(111) substrate and Rh deposit.Bimetallic electrodes consisting of noble metal substrate modified by a foreign metal deposit are still in the focus of interest in electrocatalysis starting from early publications. 1-4 Tailoring bimetallic electrodes with pronounced electrocatalytic activity compared to the activity of the substrate alone or to the both constituting metals is a demanding task regarding the chemical nature and the structure of the substrate and deposit, which should result in improved surface chemistry and geometry with respect to the active surface sites and/or to the electronic effect. Well-ordered noble metal electrodes modified by submonolayer to a few layers thick deposit of highly active metals from platinum group are the most convenient bimetallic model systems for fundamental studies of the electrocatalytic activity of such various nanostructures for fuel cell reactions. [5][6][7] Structural, electronic and chemical properties of well-defined bimetallic surfaces are examined ex situ by common techniques including Scanning Probe Microscopy (SPM), and X-ray Photoelectron Spectroscopy (XPS). 8,9 With the advent of in situ microscopic and spectroscopic techniques, such as Scanning Tunneling Microscopy (STM), 10 XPS, 11 Surface X-ray Scattering (SXS) and X-ray Absorption Spectroscopy (XAS), 12 it became possible to observe the structure of bimetallic surface and to determine its chemical composition and oxidation state of constituting metals under defined electrochemical conditions or during electrocatalytic reactions.For the preparation of bimetallic electrodes with well-defined structure, various deposition methods were employed including electrochemical deposition on nonreconstructed 13 or reconstructed single crystal surfaces, 14 surface limited redox replacement, 15-18 defectmediated growth, 19 and spontaneous deposition. 20,21 The spontaneous deposition method, which is explored in this work, assumes several processes that occur on the electrode surface during its immersion into the depositing metal ions solution at open circuit potential. These involve either irreversible adsorption of metal ion complexes or electroless deposition in which depositing metal ions are reduced by substrate atoms which are oxidized, or a combination of both. Finally obtained bimetallic surface consists of three-dimensional foreign metal nanoislands with the coverage up to a monolayer. In some cases, w...

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Section: Resultscontrasting

confidence: 56%

Section: Resultscontrasting

confidence: 56%

Section: Resultsmentioning

confidence: 88%

See 1 more Smart Citation

Spontaneously Deposited Rh on Au(111) Observed by AFM and XPS: Electrocatalysis of Hydrogen Evolution

Štrbac

Smiljanić

Rakočević

2016

J. Electrochem. Soc.

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“…For instance, even with the possibility of oxide formation, it has been demonstrated that AuxOy layers are rather unstable and prone to decomposition under UHV, suggesting the existence of a dynamic equilibrium between the oxide layer and oxygen at the gas phase 42 .…”

Section: Resultsmentioning

confidence: 99%

Promotion Effect of Platinum on Gold’s Reactivity: A High-Resolution Photoelectron Spectroscopy Study

et al. 2016

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The reactivity of the Pt/Au(332) surface was studied using high resolution photoelectron spectroscopy and carbon monoxide adsorption at 3.5 x 10 -3 mbar. The characterization of Pt/Au (332) indicates the formation of a Au-Pt surface alloy at the top most atomic layer of the (332) crystal due to an atomic exchange mechanism at both terrace and step edge. The amount of alloyed Au atoms has proven to be dependent on the amount of Pt deposited in the coverage range investigated. The activation of Au atoms by alloying is detected by comparing the ability of the surface to adsorb CO at high pressures. By analyzing the C 1s and O 1s photoemission lines it is possible to conclude that CO adsorption is both dissociative and molecular on the PtAu/Au(332) surface, differently from the behavior observed for Au and Pt single crystals. Also, by rising the temperature of the COads-PtAu/Au(332) surface, a dissociative reaction path is followed with the accumulation of graphitic carbon on the surface and the oxygen desorption. Thus, our results shows, not only the differential catalytic behavior of Pt@Au/Au(hkl) model surfaces but also that Au atoms have an active role on the reaction mechanism.

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“…The alternative way, which is associated with studying adsorbed oxygen on the pure bulk gold surface (foil, single crystals, or powders), encounters a major obstacle, namely, the difficulties of obtaining oxygen species on bulk gold due to the high energy barrier of О 2 adsorption [21,22]. Different authors proposed different techniques to treat the surface of gold and obtain chemosorbed oxygen on gold: ozone [23,24], NO 2 [25], and atomic oxygen [26,27] exposure, oxygen adsorption at high pressures and temperatures [28], etc. Other authors propose more effective approaches in terms of the degree of surface oxidation: electrochemical oxidation of a gold electrode [29], laser ablation [30], magnetron sputtering [31] in an oxygen atmosphere, and microwave [32,33] or radio-frequency [34,35] activated oxygen exposure.…”

Section: Introductionmentioning

confidence: 99%

An XPS and TPD study of gold oxide films obtained by exposure to RF-activated oxygen

2015

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Low-temperature oxidation of the polycrystalline surface of bulk metallic gold with radio-frequency activated oxygen is used to obtain oxide films, which are investigated by a combination of X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). The XPS estimate for the composition and thickness of the oxide films is close to Au 2 O 3 and is 6-10 nm. The analysis of the Au4f and O1s lines reveals only one state of the oxidized gold, which is described by E b (Au4f) = 85.5 eV, and two nonequivalent states of oxygen with E b (O1s) = 529.3 eV and 530.3 eV, which are uniformly distributed over the oxide film and may be attributed to nonequivalent oxygen states in the gold oxide structure. The thermal stability study shows that the gold oxide decomposes in one stage into metal at a temperature of T des = 530 K. According to the TPD data, the desorption activation energy is E des = 140 kJ/mol. The hightemperature oxidation of the gold surface reveals the formation of dissolved oxygen in bulk gold. This oxygen is characterized by a broad TPD peak with a maximum at T des = 800 K. This oxygen state is not detected by XPS. The concentration of dissolved oxygen is supposed to be below the XPS sensitivity threshold and is estimated at about 1% or less.

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A near ambient pressure XPS study of Au oxidation

Cited by 140 publications

References 43 publications

Spontaneously Deposited Rh on Au(111) Observed by AFM and XPS: Electrocatalysis of Hydrogen Evolution

Spontaneously Deposited Rh on Au(111) Observed by AFM and XPS: Electrocatalysis of Hydrogen Evolution

Promotion Effect of Platinum on Gold’s Reactivity: A High-Resolution Photoelectron Spectroscopy Study

An XPS and TPD study of gold oxide films obtained by exposure to RF-activated oxygen

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