Anion/Cation Layers at Electrified Interfaces: A Comprehensive STM, XRD and XPS Case Study

Pham, Duc Thanh; Keller, Hubert; Breuer, S. W.; Huemann, Sascha; Hải, Nguyễn Thanh; Zoerlein, Caroline; Wandelt, K.; Broekmann, Peter

doi:10.2533/chimia.2009.115

Cited by 15 publications

(10 citation statements)

References 12 publications

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“…It is most likely that such a fractional transformation of dication into its reduced species is caused by secondary electrons interacting with viologen dication, a strong electron acceptor . Similar multicomponent N 1s spectra involving reduction product formation were reported for various types of solid-state dichloride salts of viologens. ,,− Figure also shows the O 1s core-level spectrum. Since O 2 , as contaminants from air, tends to desorb rapidly from HOPG surfaces under UHV conditions, the O 1s spectra might be associated with the coadsorbed water at cationic sites of dPhV 2+ and dPhV •+ .…”

Section: Results and Discussionsupporting

confidence: 63%

“…The N 1s core-level spectrum (Figure ) can fit with three bands as shown. Based on literature, ,,− the peak at 401.7 eV can be ascribed to the positively charged nitrogen of the dPhV 2+ and that at 398.4 eV to the nitrogen of viologen radical cation (V •+ ) formed by X-ray excitation in the analysis chamber. The presence of the peak at 405.7 eV was also reported by Biniak and co-workers with an assignment to chemisorbed nitrogen oxide .…”

Section: Results and Discussionmentioning

confidence: 96%

“…Viologens form their adsorption layers on metal electrode surfaces, such as Hg, Au, Ag, Cu, and others. ,− It is known that dimethyl viologen, for example, exhibits various adsorption orientations on an Hg electrode depending on both its oxidation state and electrode surface charge . A soluble dialkyl viologen with long chains often exhibits a spike-like voltammetric peak pair at a less negative potential than the redox potential in the solution phase. − It has been concluded that the spike response originates from potential-driven phase transition associated with reduction of the viologen, leading to the formation of a two-dimensional (2D) condensed film of the reduced form.…”

Section: Introductionmentioning

confidence: 99%

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Diphenyl Viologen on an HOPG Electrode Surface: Less Sharp Redox Wave than Dibenzyl Viologen

Higashi

Sagara

2013

Langmuir

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Redox behavior of diphenyl viologen (dPhV) on a basal plane of a highly oriented pyrolytic graphite (HOPG) electrode was described using the results of voltammetric and electroreflectance measurements. Its characteristics were compared to those of dibenzyl viologen (dBV), which undergoes the first-order faradaic phase transition. Unlike dBV, dPhV-dication (dPhV(2+)) was found to take a strongly adsorbed state on an HOPG surface. This is due to much stronger π-π interaction between phenyl rings of dPhV(2+) and HOPG surface than between benzyl groups of dBV(2+) and the surface. The participation of this strongly adsorbed dPhV(2+) in the redox process can be avoided by (1) a shorter than ∼3 min time period elapsing from touching a freshly cleaved HOPG surface to dPhV solution until the start of potential scan, (2) complete equilibration at the electrode potentials at which superficial dPhV molecules are fully reduced, or (3) multiple cyclic potential scanning to repeat oxidation-reduction of adsorbed species. Even in such conditions, although voltammograms of thin-layer electrochemistry for the surface-confined dPhV(•+)/dPhV(2+) couple are obtained with peak widths being as narrow as those of dBV, it is not the first-order phase transition. The participation of strongly adsorbed dPhV(2+) molecules results in another new voltammetric feature with a broader peak. The film formed by strongly adsorbed dPhV(2+) was hydrophilic, whereas dBV(2+) does not form such a film but only a gas-like layer. Measurements using X-ray photoelectron spectroscopy confirmed that the film consists of dPhV(2+) with coexistent water. These results reveal a typical case that delicate interaction balance among V(2+), V(•+), and electrode surface determines whether the two-dimensional first-order transition takes place or not.

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Section: Results and Discussionsupporting

confidence: 63%

Section: Results and Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Diphenyl Viologen on an HOPG Electrode Surface: Less Sharp Redox Wave than Dibenzyl Viologen

Higashi

Sagara

2013

Langmuir

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“…The breakdown of the anion structure is commonly associated with the disappearance of positional and translational order in the OHL. 43,34 ■ CONCLUSIONS This study provides a significant extension of a new finestructure model of the electric double layer by considering the lateral ordering of interfacial water and coadsorbed cations that are attracted in the outer Helmholtz layer (OHL) by chemisorbed anions in the inner Helmholtz layer (IHL). Such a centered bilayer system (structurally coupled IHL and OHL) was necessary to reproduce all surface sensitive diffraction data, especially the adlayer and specular data which are most sensitive to the present interfacial structure.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Competitive Anion/Water and Cation/Water Interactions at Electrified Copper/Electrolyte Interfaces Probed by in Situ X-ray Diffraction

et al. 2012

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The full 3D structure of a copper/electrolyte interface is studied by means of in situ surface X-ray diffraction (SXRD) methods. Chloride anions chemisorb on Cu(100) in 10 mM HCl at high potentials under formation of a p(1 × 1)-Cl adlayer. This anionic chemisorption layer serves as a structural template for the lateral ordering of water molecules and hydronium cations in the near-surface liquid electrolyte. Evidence for this interfacial geometry is mainly derived from the intensity distribution of surface-sensitive X-ray diffraction data along the (10L)-adlayer rod. The characteristic oscillating intensity distribution along the (10L) rod is due to a centered bilayer system consisting of the anionic inner Helmholtz layer (IHL) of chemisorbed chloride and the cationic outer Helmholtz layer (OHL). The latter is constituted in the present case by hydronium cations that preferentially populate 4-fold hollow sites of the underlying chloride lattice. IHL and OHL are separated by an extra interfacial water layer. Anions and cations in the IHL and OHL compete for these water species as part of their solvation shell. The Cl/water/hydronium bilayer can be considered as a prototypical model system where the anions and cations in the coupled bilayer system are sharing the interfacial water as part of their solvation shell. In this respect, the Cl − /water/hydronium bilayer considerably differs from the previously studied Cl − /water/K + system where the interfacial water was clearly assigned to the solvation shell of the alkali metal cation in the OHL. The absence of strongly solvated alkali metal cations in the OHL leads to an increase in the in-plane and out-of-plane exchange dynamics of water and hydronium cations as manifested by an isotropic atomic displacement parameter that is notably higher for the Cl − /water/hydronium than for the more static Cl − /water/K + system. A comprehensive comparison of our results with other state-of-the-art SXRD studies strongly suggests that the adsorption of partly solvated cations on-top of an anionmodified metal electrode surface has to be considered as a specif ic cation adsorption phenomenon since the particular structure of the formed bilayer system as well as the involved interfacial dynamics clearly depend on the chemical nature of the anions and cations involved in the structure formation.

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“…After the chloride desorption, the HER occurs if no viologen molecules are on the Cl/Cu(100) surface. 40 3.2.6 Dimer phase. The surface structure of the dimer phase is shown in Fig.…”

Section: Chloride Desorptionmentioning

confidence: 99%

Molecular structures of dicarboxylated viologens on a Cu(100) surface during an ongoing charge transfer reaction

Tsay

et al. 2010

Phys. Chem. Chem. Phys.

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Molecular structures of dicarboxylated viologens (1,1'-bis (7-carboxyheptyl)-4,4'-bipyridinium dibromide molecules, V-(C(7)-COOH)(2)) on a Cu(100) surface are studied by means of in situ scanning tunneling microscopy (STM) in combination with cyclic voltammetry (CV). Self-assembled monolayers of adsorbed dicarboxylated viologens form during an ongoing charge transfer reaction. Mainly six structures of the organic molecules are observed, including a dot array, metastable phases, stripe patterns, a closed stacking stripe pattern, chloride desorption, and a dimer phase. The molecular structural models for all the structures have been successfully established. The carboxylated viologen molecules in the dicationic state prefer the face-on configuration on the surface and form the dot array phase. The other phases are shown by the radical state of the viologens. The metastable phases show two forms: cluster-like and stripe pattern-like structures. Main features of the metastable phases are face-to-face configurations of the radical viologens in π-stacking form between neighboring parallel bipyridiniums. Hydrogen bonding is considered to be the major factor in constructing the network of the stripe pattern. At a more negative potential, the bilayers of the stripe pattern transform to be a monolayer of the closed stacking stripe pattern because of the enhanced electrostatic force. The closed stacking stripe pattern is stable on the surface until chloride desorption. As the chloride anions desorb from the Cu(100) surface, the disordered dimers transform to an ordered dimer phase on a Cu(100)-1×1 surface due to the hydrogen bonding between neighboring dimer rows.

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Anion/Cation Layers at Electrified Interfaces: A Comprehensive STM, XRD and XPS Case Study

Cited by 15 publications

References 12 publications

Diphenyl Viologen on an HOPG Electrode Surface: Less Sharp Redox Wave than Dibenzyl Viologen

Diphenyl Viologen on an HOPG Electrode Surface: Less Sharp Redox Wave than Dibenzyl Viologen

Competitive Anion/Water and Cation/Water Interactions at Electrified Copper/Electrolyte Interfaces Probed by in Situ X-ray Diffraction

Molecular structures of dicarboxylated viologens on a Cu(100) surface during an ongoing charge transfer reaction

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