Coverage of the Cd Underpotential Deposited Layer Formed on an Au(111) Substrate

Kawamura, Hiroyuki; Takahasi, Masamitu; Мizuki, J.

doi:10.1149/1.1512671

Cited by 18 publications

(8 citation statements)

References 16 publications

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“…Since the Os islands are morphologically rough (see smaller-scale images below), the precise height of Os was not determined well enough to distinguish Os from Au based only on the apparent height. Indeed, alloy formation with Au(111) has been observed previously after the electrodeposition of Pb, 34,35 Cd, [36][37][38][39][40][41][42] and Sb [43][44][45][46] noble metal Pt was deposited on Au(111) at room temperature and formed a 0.03 ML alloy followed by the formation of mixed Pt-Au islands. 47 Thus, the formation of an Au-Os alloy seems possible and it is the best explanation for the unexpectedly high coverage of islands.…”

Section: Resultsmentioning

confidence: 86%

In Situ STM Study of Au(111)/Os Bimetallic Surfaces: Spontaneous Deposition and Electrochemical Dissolution

2005

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We provide an electrochemical and structural characterization by in situ STM of Au(111)/Os electrodes prepared by spontaneous deposition of Os on Au(111). Surfaces with Os coverage values up to the saturation coverage were examined, from 10%. Using comparisons to previous work on Au(111)/Ru, Pt(111)/Ru, and Pt(111)/Os, we find that we may now generalize that Os deposits spontaneously faster than Ru and has a greater tendency to form 3-D structures. Additionally, the Au(111) substrate shows preferential step and near-step decoration in both cases, although it is less pronounced for Os than Ru. We also investigated the incremental dissolution of the Os from Au(111), to better understand electrochemical dissolution processes in general and to better control the Os deposit structure. The application of controlled electrochemical treatments (cyclic voltammetry up to increasingly positive values) significantly increased the dispersion of the Os deposit by generating smaller, more widely spaced islands. Upon voltammetry up to 0.75 V, the Au(111)/Os surface showed evidence of alloying and the formation of 3-D structures suggestive of strong Os-Os (oxidized) species interactions. The CO stripping results show the Au(111)/Os is not particularly effective for this reaction, but such results help to complete the overall picture of NM-NM catalytic combinations. Although the Au(111)/Os system itself is not catalytically active, the electrochemical manipulation of the deposit structure demonstrated here may be applied to other noble metal/noble metal (NM/NM) catalytic substrates to find optimal deposit morphologies.

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Section: Resultsmentioning

confidence: 86%

In Situ STM Study of Au(111)/Os Bimetallic Surfaces: Spontaneous Deposition and Electrochemical Dissolution

2005

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“…25 According to results reported for Cd/Au(111), the coverage of Cd varied between 0.4 and 0.66, which is substantially higher than that (θ ) 0.17) of Cd/Rh(111). 31,32 This thought could also hold for the coadsorbed anions of (bi)sulfate, whose coverage differ on these two surfaces. 31,32 These anionic species which are intermediates in the interactions between Cd adatoms also contributed to the arrangements of Cd deposit.…”

Section: Discussionmentioning

confidence: 99%

“…31,32 This thought could also hold for the coadsorbed anions of (bi)sulfate, whose coverage differ on these two surfaces. 31,32 These anionic species which are intermediates in the interactions between Cd adatoms also contributed to the arrangements of Cd deposit.…”

Section: Discussionmentioning

confidence: 99%

Role of the Anion in the Underpotential Deposition of Cadmium on a Rh(111) Electrode: Probed by Voltammetry and in Situ Scanning Tunneling Microscopy

et al. 2005

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In situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV) were employed to examine the underpotential deposition (UPD) of cadmium on a rhodium(111) electrode in sulfuric and hydrochloric acids. The (bi)sulfate and chloride anions in the electrolytes played a main role in controlling the number and arrangement of Cd adatoms. Deposition of Cd along with hydrogen adsorption occurred near 0.1 V (vs reversible hydrogen electrode) in either 0.05 M H2SO4 or 0.1 M HCl containing 1 mM Cd(ClO4)2. These coupled processes resulted in an erroneous coverage of Cd adatoms. The process of Cd deposition shifted positively to 0.3 V and thus separated from that of hydrogen in 0.05 M H2SO4 containing 0.5 M Cd2+. The amount of charge (80 microC/cm2) for Cd deposition in 0.5 M Cd2+ implied a coverage of 0.17 for the Cd adatoms, which agreed with in situ STM results. Regardless of [Cd2+], in situ STM imaging revealed a highly ordered Rh(111)-(6 x 6)-6Cd + HSO4- or SO42- structure in sulfuric acid,. In hydrochloric acid, in situ STM discerned a (2 x 2)-Cd + Cl structure at potentials where Cd deposition commenced. STM atomic resolution showed roughly one-quarter of a monolayer of Cd adatoms were deposited, ca. 50% more than in sulfuric acid. Dynamic in situ STM imaging showed potential dependent, reversible transformations between the (6 x 6) Cd adlattices and (square root 3 x square root 7)-(bi)sulfate structure, and between (2 x 2) and (square root 7 x square root 7)R19.1 degrees -Cl structures. The fact that different Cd structures observed in H2SO4 and HCl entailed the involvement of anions in Cd deposition, i.e. (bi)sulfate and chloride anions were codeposited with Cd adatoms on Rh(111).

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“…The specific adsorption of sulfate anions during the Cd UPD on Au(111) was also suggested on account of specular X-ray reflectivity results. [12] It was demonstrated that the coverage of the Cd UPD layer increases with increasing sulfate anion solution concentration, but from these experiments the involved surface alloying was not clear. A surface alloy formation process was observed [13 -16] in the system Au(100)/Cd 2+ , SO 4 2− and it was concluded that, in this case, the Au-Cd surface alloy is formed during the UPD phenomenon probably by a turnover process between the adsorbed Cd atoms and the underlying Au atoms, with a subsequent solid-state diffusion of these atoms through the alloyed phase.…”

Section: Introductionmentioning

confidence: 88%

New insights on the Cd UPD on Au(111)

Barrio

García

Mayer

et al. 2008

Surface & Interface Analysis

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Coverage of the Cd Underpotential Deposited Layer Formed on an Au(111) Substrate

Cited by 18 publications

References 16 publications

In Situ STM Study of Au(111)/Os Bimetallic Surfaces: Spontaneous Deposition and Electrochemical Dissolution

In Situ STM Study of Au(111)/Os Bimetallic Surfaces: Spontaneous Deposition and Electrochemical Dissolution

Role of the Anion in the Underpotential Deposition of Cadmium on a Rh(111) Electrode: Probed by Voltammetry and in Situ Scanning Tunneling Microscopy

New insights on the Cd UPD on Au(111)

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