Underpotential Deposition Of Lead Research Articles

Investigation of the Underpotential Deposition of Lead on Gold in Basic and Acidic Room-Temperature Chloroaluminate Molten Salts†

Investigation of the Underpotential Deposition of Lead on Gold in Basic and Acidic Room-Temperature Chloroaluminate Molten Salts†

Underpotential Deposition of Lead onto Pt(001): Interface Structure and the Influence of Adsorbed Bromide

Using in-situ X-ray diffraction, we have studied the underpotential deposition of Pb onto a Pt(001) electrode both in pure perchloric acid and in the presence of bromide anions. In pure perchloric acid, the Pb adlayer forms monolayer-high islands which fully cover the Pt surface but have no long range order in the surface plane. The presence of strongly adsorbed Br atoms at step edges on the Pt(001) surface and the competitive nature of the Pb−Br interaction cause a rapid exchange of Pb and Br on the Pt terraces, the Pb then forming a strongly bonded c(2×2) adlayer.

Investigation of Lead Underpotential Deposition on Silver Substrate in Magnetically Treated Electrolyte

Investigation of Lead Underpotential Deposition on Silver Substrate in Magnetically Treated Electrolyte

Underpotential deposition of lead on polycrystalline platinum and its influence on the oxygen reduction reaction

This work describes the study of underpotential deposition ( upd) of Pb on polycrystalline platinum in 0.2M HClO 4 solutions using cyclic voltammetry and rotating ring-disk electrode techniques. In such conditions, a full monolayer of upd Pb corresponds to a coverage of 0.41. The adsorption of lead inhibits the adsorption of hydrogen in a non-selective way. This behaviour was explained through the comparison between the radius of the ad-atom and the substrate. It was calculated that each Pb ad-atom occupies two sites in the surface. Additionally it is shown that the presence of upd Pb significantly inhibits the oxygen reduction reaction. This effect associated to the formation of H 2O 2 as the final product, instead of H 2O.

In situ atomic force microscope study of lead underpotential deposition on gold (111): structural properties of the catalytically active phase

Atomic resolution atomic force microscope (AFM) images of Pb underpotential deposition on Au(111) electrodes are presented. Pb grows on the Au(111) surface by forming islands which are initially one Pb adatom high (0.30 nm) but which rapidly grow in height to 0.53 nm through association of the Pb with solvent or hydroxide. The Pb aggregates have a hexagonal close-packed atomic structure exhibiting an atom-atom spacing of 0.35±0.03 nm. The islands can be easily swept away by the AFM tip when the tip sample force is set at 80 nN, but Pb deposited at step edges is not swept away under these conditions. This suggests that the Pb (island)-Au interaction is relatively weak

Investigation of the quenching of surface enhanced Raman scattering from pyridine on copper and silver electrodes by underpotential deposition of lead

Investigation of the quenching of surface enhanced Raman scattering from pyridine on copper and silver electrodes by underpotential deposition of lead

Adsorption and underpotential deposition of lead at electrodeposited platinum electrodes

The underpotential deposition (UPD) of lead at electrodeposited platinum electrodes has been studied using the electrochemical quartz crystal microbalance (EQCM). At higher values of [Pb 2+] mass responses accompanying cyclic voltammetric experiments reveal large mass changes as the UPD deposit develops and is stripped but, when [Pb 2+] is low, subtraction of the response seen for platinum in the absence of UPD reveals that the UPD process is not at equilibrium under the conditions used and continues developing over the potential range between 0.45 V and −0.3 V. Mass responses to simple injection experiments reveal the presence of adsorbed Pb 2+ on oxidized electrodes. Coverage of Pb ads 2+ increases with potential between 0.9 V and 1.2 V and approaches 0.09 when [Pb 2+]= 2 mM and E = 1 V. UPD of lead at platinum thus involves a combination of discharge of adsorbed species and reduction of lead ions from solution. UPD coverages were determined over a wide range of potential from mass transients resulting from potential steps and the injection of Pb 2+ into the electrolyte. The isotherm obtained agrees well with previously published data and demonstrates that EQCM mass data can be used for the estimation of UPD coverages.

New aspects in underpotential-overpotential transitions in metal deposition processes

Previous electrochemical results obtained by transient measurements and morphological studies of the lead underpotential and overpotential deposition on both electrolytically grown quasi-perfect and real Ag(100) and Ag(111) single crystal faces as well as new information obtained by in situ GIXS (grazing incidence X-ray scattering) are quantitatively interpreted by a new physical model. The nucleation process is assumed to be influenced by compressive strain in the UPD adlayer which arises from a strong substrate-adsorbate interaction.

New aspects in underpotential-overpotential transitions in metal deposition processes

Abstract Previous electrochemical results obtained by transient measurements and morphological studies of the lead underpotential and overpotential deposition on both electrolytically grown quasi-perfect and real Ag(100) and Ag(111) single crystal faces as well as new information obtained by in situ GIXS (grazing incidence X-ray scattering) are quantitatively interpreted by a new physical model. The nucleation process is assumed to be influenced by compressive strain in the UPD adlayer which arises from a strong substrate-adsorbate interaction.

単結晶銀上への鉛のＵｎｄｅｒｐｏｔｅｎｔｉａｌ Ｄｅｐｏｓｉｔｉｏｎ過程のＩｎ Ｓｉｔｕ観測；光音響的手法によるアプローチ

単結晶銀上への鉛のＵｎｄｅｒｐｏｔｅｎｔｉａｌ Ｄｅｐｏｓｉｔｉｏｎ過程のＩｎ Ｓｉｔｕ観測；光音響的手法によるアプローチ

Anisotropic nonlinear optical response from silver electrodes during thin-film deposition

Rotational anisotropy in the optical second harmonic generation from Ag(111) and Ag(110) single-crystal electrodes is used to measure relative changes in the components of the nonlinear susceptibility of the interface during charging and adsorption processes. The application of a dc field and underpotential deposition of lead and thallium are studied.

Tracking anion expulsion during underpotential deposition of lead at silver using the quartz microbalance

Variations in the electrode mass, charge and pseudocapacitance current have been studied as a function of potential during the underpotential deposition (UPD) of lead at a silver electrode in alkaline solutions. The rotating disk electrode and in situ quartz crystal microbalance (EQCM) techniques were used. New, interesting phenomena have been discovered. Customarily, UPD is ascribed to discharge of dissolved metal ions, and a mass increase would accompany such a UPD process. Surprisingly, a decrease in the weight of the electrode occurred during the entire cathodic process for Pb UPD, rather than an increase in weight that would be expected for a UPD process involving a dissolved Pb(II) species. We found that during the Pb UPD formation process, the entire cathodic charge is transferred to a Pb(II) ads species which is already present on the surface as an adsorbed monolayer. We attribute the observed decrease in mass to OH − expulsion from the electrode surface. At potentials more negative than the region for Pb UPD formation, an increase in mass not associated with any cathodic current was observed. This mass increase is caused by the adsorption of a Pb(II) species on a Pb UPD monolayer. Thus, the charge transfer process for formation of an underpotential lead deposit and the increase in electrode mass do not coincide at a silver substrate. A different mechanism is observed for Pb UPD at gold. The combination of EQCM and voltammetric measurements is a powerful means of elucidating UPD mechanisms and tracking expulsion of ligands from the electrode surface.

ChemInform Abstract: Anion Effects on the Underpotential Deposition of Lead on Cu(111)

Abstracthave been investigated in solutions containing perchlorate, acetate, or chloride (pH 1.5‐3.55) by voltammetric and complex potential controlled perturbation techniques.

Anion effects on the underpotential deposition of lead on Cu(111)

The underpotential deposition of lead on Cu(111) single crystal surfaces was studied in aqueous solutions containing different anions such as perchlorate, acetate, and chloride at various pH within the range 1.5 ⩽ pH ⩽ 3.55 using voltammetric and complex potential controlled perturbation techniques. The UPD of lead appears to be a highly irreversible process which depends on pH, the electrical history of the metal—electrolyte interface and the type of anions present in the electrolyte. A critical threshold potential for the cathodic monolayer formation is revealed by the cyclic voltammogramms as well as by the charge isotherms. The nucleation like behaviour is interpreted in terms of a negative 2-D nucleation and growth process within a preformed surface layer consisting of specifically adsorbed anions or oxygen containing species.

In Situ X-ray diffraction studies of electrode solution interfaces

A computer controlled X-ray diffraction system utilizing position sensitive photon counting techniques that is capable of investigating, in situ, structure at the solid/liquid interface, particularly that between an electrode and an electrolyte solution, is described. The application of this technique to the study of iodine adsorption on graphite, hydride formation at nickel electrodes, the electrochemical interconversion of nickel hydroxides and oxyhydroxides and the structural changes accompanying lead underpotential deposition on silver electrodes is discussed.

ChemInform Abstract: Influence of Adsorbing Substances on the UPD of Lead onto the (111)‐Oriented Silver Single Crystal Surface. Part 2.

AbstractThe kinetics of UPD (underpotential deposition) of Pb on an Ag single crystal were investigated in the presence of Cl04‐ , AcO′ and the citrate anion by potential step measurements rendering Current ‐ time transients.

Potential dependence of lead and silver underpotential coverages in acetonitrile using a piezoelectric crystal oscillator method

The underpotential deposition of lead and silver on gold was studied in acetonitrile as a solvent. The rde, the rrde and the quartz crystal microbalance techniques were used. Satisfactory agreement for the coverage values as a function of underpotential were obtained among the rotating electrode and the quartz crystal balance methods.

Underpotential deposition of lead on gold single crystal faces: Part II. General discussion

A general discussion of lead UPD on gold faces is given. The electrosorption valency is determined by a simple experimental method. The effect of reconstruction of the substrate is discussed for the (100) gold face. Understanding of the cyclic voltammograms is achieved thanks to the comparison with the results obtained in UHV. Observation of the UPD region gives the energy spectrum of the faces.

Underpotential deposition of lead on single crystal faces of gold Part I. The influence of crystallographic orientation of the substrate

The influence of the crystallographic orientation of the gold substrate surface on lead deposition and removal in the underpotential region is studied in detail. In order to observe systematic changes in the cyclic voltammograms, the faces of the three main zones of the unit projected stereographic triangle are grouped into five sections following bond order notation or a notation based on the TLK model of the surfaces. Correlations with the potential of zero charge are discussed. A comparison with ionic adsorption is made.

Underpotential deposition of lead on single crystal faces of gold: Part I. The influence of crystallographic orientation of the substrate

The influence of the crystallographic orientation of the gold substrate surface on lead deposition and removal in the underpotential region is studied in detail. In order to observe systematic changes in the cyclic voltammograms, the faces of the three main zones of the unit projected stereographic triangle are grouped into five sections following bond order notation or a notation based on the TLK model of the surfaces. Correlations with the potential of zero charge are discussed. A comparison with ionic adsorption is made.