On the Stability of Ag/Au(111) Expanded Structures

Sánchez, Cristián G.; Dassie, Sergio Alberto; Leiva, E.P.M.

doi:10.1021/la020312a

Cited by 11 publications

(7 citation statements)

References 23 publications

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“…In contrast, the electrodeposition of less than 1 monolayer of Ag onto the Au(111) surface produces open structures, as previously shown. − However, a series of first-principle calculations by Sanchez et al. showed that no structure more expanded than a (1 × 1) compact monolayer is more stable than a bulk Ag deposit and hence UPD of Ag should not occur on Au(111) . In order to explain the discrepancy between the calculations and the experimental results, it was suggested that adsorbed Ag may generate a large shift in the work function thus inducing a negative shift in the potential of zero charge ( pzc ) and resulting in the additional adsorption of anions and a change in the Au–Ag binding energy.…”

Section: Discussionmentioning

confidence: 93%

“…35−40 However, a series of first-principle calculations by Sanchez et al showed that no structure more expanded than a (1 × 1) compact monolayer is more stable than a bulk Ag deposit and hence UPD of Ag should not occur on Au(111). 41 In order to explain the discrepancy between the calculations and the experimental results, it was suggested that adsorbed Ag may generate a large shift in the work function thus inducing a negative shift in the potential of zero charge (pzc) and resulting in the additional adsorption of anions and a change in the Au−Ag binding energy. The open structures observed during the electrodeposition of Ag onto Au(111) are dependent on the anion present; for example, in the presence of sulfate, the Ag UPD overlayer exhibits a (3 × 3) structure, in the presence of nitrate, a (4 × 4) structure, and in pure perchlorate electrolyte, another open structure.…”

Section: Discussionmentioning

confidence: 99%

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Structure and Stability of Underpotentially Deposited Ag on Au(111) in Alkaline Electrolyte

2016

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A combination of in situ surface X-ray scattering (SXS) and cyclic voltammetry (CV) measurements have been performed to understand the structure and behavior of underpotentially deposited (UPD) Ag layers on Au(111) following transfer of the electrode to alkaline electrolyte (0.1 M KOH). UPD of Ag from 0.05 M H 2 SO 4 + 1 mM Ag 2 SO 4 electrolyte was used to form a monolayer and bilayer film of Ag on Au(111) before immersion into 0.1 M KOH electrolyte. Analysis of the SXS data shows that, while the bilayer Ag film is stable upon transfer to the alkaline electrolyte, the Ag monolayer film reorders to a partial bilayer structure upon or during the transfer process. The Ag-modified Au(111) electrode shows a potential response for OH − adsorption that is similar to that of Ag single crystal electrode surfaces.

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Structure and Stability of Underpotentially Deposited Ag on Au(111) in Alkaline Electrolyte

2016

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“…5, the underpotential shift ΔE upd defined at the beginning of this chapter can be estimated from two calculations: the binding energy of the adsorbate M to the substrate S and the cohesive energy of bulk M. This is a good approximation for compact adsorbates and in those cases where the work function difference between bulk M and bulk S is small. In the first case, this so because in the case of compact upd adsorbates, adatoms present a larger depolarization [199], so that solvation effects should be smaller and may be neglected. Figure 3.27 shows effective dipole moments of Ag atoms adsorbed on …”

Section: ð3:54þmentioning

confidence: 99%

Phenomenology and Thermodynamics of Underpotential Deposition

Oviedo

Reinaudi

García

et al. 2015

Underpotential Deposition

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As can be found from the other chapters of this book, underpotential deposition shows a wide variety of behaviors, which involve the occurrence of several surface phases, formation of submonolayers, monolayers (ML) and eventually the formation of bilayers. Adsorption may be commensurate or incommensurate, where the ML may undergo compression, and metal adatoms may coadsorb with anions to generate new phases. To start the discussion and briefly go into the history of the development of thermodynamic models for upd, we consider a relatively "simple" system, as shown in Fig. 3.1, which corresponds to Ag deposition on Pt(111) [1]. The voltammogram of this system presents three cathodic and three anodic peaks, which correspond to ML formation/desorption(3), bilayer formation/desorption(2) and bulk deposition/oxidation(1) of Ag. The peak potentials of the complementary processes do not coincide, denoting that at the present sweep rate a quasi equilibrium state has still not been reached. For the discussion below, we choose the anodic peaks, that we will denote with E 1 , E 2 and E 3 (see Fig. 3.1). At the sight of the features of this voltammogram, and although the abscissa axis gives a measure for the electrochemical potential of electrons at the working electrode, it may be appealing to use the position of the peaks found for this system as a measure for the stability of the different upd ad-phases being formed. In this spirit, Kolb et al. [2][3][4] introduced in the 1970s the concept of underpotential shift, ΔE upd . This quantity was defined as the difference in the potential of the desorption peak for a layer of a metal M adsorbed on a foreign substrate S and the potential of the peak corresponding to the dissolution of the pure metal M. In the present case, ΔE upd ¼ E 3 À E 1 , as marked in the red segment in Fig. 3.1. At the time Kolb et al. developed their modeling of upd, single crystal surfaces were not available for performing electrochemical experiments, so that all the data employed by these authors were restricted to polycrystalline surfaces. On the basis

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“…8 First principles density functional theory (DFT) has been applied to obtain atomistic insights into the stability and structure of the metal monolayers achieving varying degrees of correspondence with experimental voltammetry. [9][10][11][12][13][14][15] These calculations are typically performed in the absence of a solvent; however, key features of the interface such as anion co-adsorption have been included when warranted, leading to enhanced descriptions of the interface. 14,15 Entropic effects have additionally been considered to obtain surface chemical potentials by including ideal configurational entropy or by fitting an Ising-like Hamiltonian to DFT results and subsequently performing grand canonical Monte Carlo calculations.…”

Section: Introductionmentioning

confidence: 99%

Voltage-dependent cluster expansion for electrified solid-liquid interfaces: Application to the electrochemical deposition of transition metals

Weitzner

Dabo

2017

Phys. Rev. B

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The detailed atomistic modeling of electrochemically deposited metal monolayers is challenging due to the complex structure of the metal-solution interface and the critical effects of surface electrification during electrode polarization. Accurate models of interfacial electrochemical equilibria are further challenged by the need to include entropic effects to obtain accurate surface chemical potentials. We present an embedded quantum-continuum model of the interfacial environment that addresses each of these challenges and study the underpotential deposition of silver on the gold (100) surface. We leverage these results to parameterize a cluster expansion of the electrified interface and show through grand canonical Monte Carlo calculations the crucial need to account for variations in the interfacial dipole when modeling electrodeposited metals under finite-temperature electrochemical conditions.

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On the Stability of Ag/Au(111) Expanded Structures

Cited by 11 publications

References 23 publications

Structure and Stability of Underpotentially Deposited Ag on Au(111) in Alkaline Electrolyte

Structure and Stability of Underpotentially Deposited Ag on Au(111) in Alkaline Electrolyte

Phenomenology and Thermodynamics of Underpotential Deposition

Voltage-dependent cluster expansion for electrified solid-liquid interfaces: Application to the electrochemical deposition of transition metals

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