Scanning Tunneling Microscopy, Fourier Transform Infrared Reflection−Absorption Spectroscopy, and X-ray Photoelectron Spectroscopy of Thiourea Adsorption from Aqueous Solutions on Silver (111)

Brunetti, Verónica; Blum, B.; Salvarezza, Roberto Carlos; Arvía, Alejandro Jorge; Schilardi, Patricia Laura; Cuesta, Ángel; Gayone, J. E.; Zampieri, G.

doi:10.1021/jp0209695

Cited by 22 publications

(52 citation statements)

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“…This work deals with the electrochemical processes at gold j TU-containing and gold j FDS-containing aqueous acid interfaces over the range of potentials related to the thermodynamic stability of water. Conclusions from the participation of TU electrosorption reactions are derived from data resulting from different electrochemical techniques, which can be contrasted with STM patterns of TU on gold (1 1 1) [2,22]. Likewise, conclusions about product formation and reactant disappearance that are reported in this work have been confirmed by in situ FTIRS data [21].…”

Section: Introductionsupporting

confidence: 52%

“…9b), the electro-oxidation voltammogram shows peaks at approximately 1.25 and 1.45 V. The former tends to decrease and shifts positively as t ad is increased, whereas the latter exhibits no potential shift, but increases with t ad . In this case, q ad increases from approximately 390 mC cm (2 to approximately 600 mC cm (2 as t ad is changed from 15 to 900 s.…”

Section: Voltammetric Electro-oxidation Of Tu Adsorbatesmentioning

confidence: 85%

“…In recent years, interest in the electrochemical processes at different metal j thiourea (TU)-containing aqueous solution interfaces has increased both for the understanding of fundamental aspects of electrochemical interfaces involving sulphur-containing molecules on single crystal metal surfaces [1,2] and for the determination of the properties of TU as an additive in different technological applications. At low concentrations, TU is used as an additive in the electrodeposition of metals such as copper from acid solutions [3], whereas, at high concentrations, it is considered as a possible leachant in hydrometallurgy for the recovery of gold and silver from minerals [4 Á/10].…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical processes at gold∣thiourea-containing aqueous acid solution interfaces

Bolzán

Piatti

Arvía

2003

Journal of Electroanalytical Chemistry

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The electrochemical behaviour of thiourea (TU) on gold in acid solutions is investigated in the range (/0.2 to 1.7 V (versus standard hydrogen electrode) by conventional and triangularly potential modulated voltammetry, rest potential (E rest ) measurements, rotating disk and rotating ring-disk techniques. The value of E rest is determined by an electrochemical reaction involving formamidine disulphide (FDS), adsorbed TU and soluble [Au(TU) 2 ] ' species. For TU concentrations (c TU ) in the range 1 0/c TU 0/50 mM, E rest decreases linearly with log c TU with a slope of approximately (/0.090 V decade (1 , while in the range 0.1 0/ c TU 0/0.25 mM, it approaches (/0.120 V decade (1 . Conventional and triangularly modulated voltammetry data indicate the quasireversible adsorption of TU occurring in the range (/0.2 0/E 0/0.1 V, and the electro-oxidation of TU to FDS in the range 0.20/ E 0/0.9 V, occurring simultaneously with the electrodissolution of gold yielding soluble [Au(TU) 2 ] ' species. Both the electrooxidation of TU and the electrodissolution of gold are under mass transfer control influenced by adsorbate formation. Different adsorbates from TU are produced depending on the adsorption potential and time. The electro-oxidation of these adsorbates in the range 0.9 Á/1.7 V yields sulphate, carbon dioxide and CN residues. Reaction products are consistent with previous STM and FTIRS data. Comparative electrochemical data from FDS-and sulphide-containing solutions are also presented. Reaction pathways in which the participation of different adsorbates is considered, are discussed.

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Section: Introductionsupporting

confidence: 52%

Section: Voltammetric Electro-oxidation Of Tu Adsorbatesmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Electrochemical processes at gold∣thiourea-containing aqueous acid solution interfaces

Bolzán

Piatti

Arvía

2003

Journal of Electroanalytical Chemistry

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“…On the other hand, a surface redox process at potentials between 0.60 and 0.90 V RHE for gold electrodes in acidic TU-containing solutions has been related to the deprotonation of adsorbed TU to form adsorbed thioureate species [17]. Note that this proposal is connected to previous suggestions regarding the existence of a deprotonation process leading to the formation of adsorbed thioureate on platinum [26], copper [27,28] and gold [29] electrodes that would involve the tautomeric form of the TU molecule…”

Section: Accepted M Manuscriptsupporting

confidence: 65%

On the electrochemical behavior of formamidine disulfide on gold electrodes in acid media

Cheuquepán

Orts

Rodes

2016

Journal of Electroanalytical Chemistry

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Please cite this article as: William Cheuquepán, José Manuel Orts, Antonio Rodes, On the electrochemical behavior of formamidine disulfide on gold electrodes in acid media, Journal of Electroanalytical Chemistry (2016Chemistry ( ), doi: 10.1016Chemistry ( /j.jelechem.2016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT ABSTRACTThe adsorption and reactivity of formamidine disulfide (FDS) was studied at gold single crystal and thin film electrodes in perchloric acid solutions and the results of cyclic voltammetry and in situ infrared spectroscopy (SNIFTIR and ATR-SEIRAS) experiments compared with those previously obtained with thiourea (TU). In addition, optimized geometries and theoretical harmonic vibrational frequencies were obtained for adsorbed FDS, TU and thioureate from plane-wave DFT calculations using periodic surface models. These results were compared in the case of TU and thioureate to those previously obtained with a model Au cluster surface with (111) orientation. In the case of FDS, weak adsorption takes place with the S-S bond essentially parallel to the metal surface. No specific bands for adsorbed FDS can be identified in the experimental ATR-SEIRA spectra. These latter spectra suggest that adsorbed thioureate species are spontaneously formed upon dissociative adsorption of FDS when dosing this molecule at open circuit. Some of the adsorbed thioureate species undergo reductive protonation giving rise to a mixed adlayer formed by adsorbed thioureate and thiourea in a surface process which is faster when a controlled potential of 0.70 V is applied. In agreement with the observations reported when dosing TU, the ratio between TU and thioureate adsorbates is found to depend on the electrode potential, being higher for potentials close to the hydrogen evolution limit and decreasing for higher potential values. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT2 Graphical AbstractHighlights -FDS adsorbs weakly on Au with Au-S distances longer than those for TU and thioureate.-Physisorbed FDS dissociates homolitically to yield adsorbed thioureate.-Some adsorbed thioureate species are reduced to adsorbed thiourea.-Dosing conditions influence the rate of formation of adsorbed thiourea.-The thiourea/thioureate adsorbate ratio depends on the applied potential.

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“…It is also known to undergo slow decomposition in aqueous solutions as a result of which sulfur-containing impurities are formed [6,7]. These impurities, when adsorbed on the electrode surface, greatly influence its electrochemical behaviour [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Using an electrode with renewable surface for study of silver reduction from acid thiourea solutions

Zelinsky

Ershov

2007

J Appl Electrochem

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Sulfur-containing thiourea (TU) decomposition products exert a considerable effect on the silver electroreduction rate in TU solutions. The technique of removing a thin layer from a metal electrode in-situ at a fixed electrode potential makes it possible to minimize the influence of adsorbed impurities on the rate of the process under study. The values of the exchange current and transfer coefficient for silver reduction from TU solutions have been determined using this technique. Impurities in acid TU solution substantially increase the reduction rate for potentials more positive than about -0.5 V vs. Ag/AgCl.

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Scanning Tunneling Microscopy, Fourier Transform Infrared Reflection−Absorption Spectroscopy, and X-ray Photoelectron Spectroscopy of Thiourea Adsorption from Aqueous Solutions on Silver (111)

Cited by 22 publications

References 61 publications

Electrochemical processes at gold∣thiourea-containing aqueous acid solution interfaces

Electrochemical processes at gold∣thiourea-containing aqueous acid solution interfaces

On the electrochemical behavior of formamidine disulfide on gold electrodes in acid media

Using an electrode with renewable surface for study of silver reduction from acid thiourea solutions

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