Anodic behavior of gold in acid thiourea solutions: A cyclic voltammetry and quartz microgravimetry study

Shevtsova, O. N.; Bek, R. Yu.; Zelinskii, A. G.; Vais, Abhitosh

doi:10.1134/s1023193506030050

Cited by 9 publications

(4 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The interaction of cyano-ligands with gold is of interest both from a fundamental perspective and, as such species may be intermediates in mineral processing circuits. In our studies of the acid thiourea leaching of gold we identified the formation of a cyanospecies at oxidizing potentials (1): electrochemical studies have determined that a species formed at high potentials has a catalytic effect on the thiourea leaching of gold (2).…”

Section: Introductionmentioning

confidence: 99%

A Spectroelectrochemical Investigation of the Interaction of Gold with Cyano-Containing Ligands

Parker

Hope

2010

ECS Trans.

View full text Add to dashboard Cite

Surface-enhanced Raman spectroelectrochemical (SERS) investigations of cyanamide, cyanoacetamide and malononitrile interaction with a roughened gold electrode were undertaken. The reagents were readily adsorbed on the surface and large shifts in the C≡N stretch band were observed on adsorption. The C≡N frequency underwent Stark tuning as the potential was scanned and, at high potentials, bands consistent with an oxidized gold complex were observed. It did not appear that the cyano functional group dissociated from the ligands and, together with the large shift in the C≡N stretch frequency on adsorption, this is indicative of π-type coordination. The 1st and subsequent voltammetric cycles in the malononitrile system showed quite different characteristics, indicative of bonding of only one of the two nitriles of the molecule to the gold surface during the 1st oxidation sweep, followed by bonding of both the nitriles in subsequent sweeps.

show abstract

Section: Introductionmentioning

confidence: 99%

A Spectroelectrochemical Investigation of the Interaction of Gold with Cyano-Containing Ligands

Parker

Hope

2010

ECS Trans.

View full text Add to dashboard Cite

show abstract

“…In this case, the effective values of the transfer coefficient and the reaction order with respect to the ligand are extremely low (α ≅ 0,1 and p ≅ 0.2). Later, quartz-crystal microbalance studies of the mechanism of anodic dissolution of gold [3,4] confirmed that under clean conditions, gold is not virtually dissolved in thiocarbamide solutions in this potential range.…”

Section: Introductionmentioning

confidence: 86%

“…In [1][2][3][4], the mechanism of anodic dissolution of gold in acidic thiocarbamide electrolytes was studied. These processes were shown to exhibit certain specific features.…”

Section: Introductionmentioning

confidence: 99%

The microbalance determination of kinetic parameters of anodic dissolution of gold in thiocarbamide electrolytes in the presence of sulfide ions

Shevtsova

Bek

Rogozhnikov

2008

2008 Third International Forum on Strategic Technologies

View full text Add to dashboard Cite

As shown by quartz-crystal microbalance measurements, in the potential range from 0.0 to 0.55 V (NHE) sulfide ions adsorbed on the gold electrode surface accelerate the electrode reaction of anodic dissolution of gold in acidic thiocarbamide solutions. The microbalance determination of kinetic parameters at a constant electrode surface coverage with sulfide ions includes a special procedure developed for the determination of the gold dissolution rate. The conditions (the potential range and the potential scan rate) of independence of the dissolution rate from the diffusion limitations associated with the ligand delivery is determined. Under these conditions, the polarization curve is shown to be linear on semilogarithmic coordinates and correspond to the Tafel equation. In this potential range, the transfer coefficient α and the reaction order with respect to the ligand p are determined at a constant electrode surface coverage θ with adsorbed sulfide ions. It is shown that with the transition from the surface coverage with sulfide ions θ = 0.1 to θ = 0.8, the transfer coefficient α changes from 0.25 to 0.55, the exchange current (i 0 ) changes from 10 -5 to 5 x 10 -5 A/cm 2 , and the effective reaction order p with respect to the ligand changes from 0.2 to 1.3. The mentioned changes are associated not only with the acceleration of gold dissolution in the presence of chemisorbed sulfide ions but also with the changeover in the mechanism of this process. Quartz-crystal microbalance data on the gold dissolution rate qualitatively agree with the results of voltammetric measurements of a renewable gold electrode. A possible version of explanation of the catalytic effect of sulfide ion adsorption on the gold dissolution is put forward.

show abstract

“…Thiourea (TU) is a model sulfur-containing species that can strongly adsorb onto a gold surface, leading to the electrochemical dissolution of gold. − The electrochemical behavior of gold in acidic thiourea has attracted attention from both scientific and technological viewpoints. − Anodic dissolution of Au occurs in the potential range of 0.45–0.60 V (vs RHE), which is approximately 0.6 V less positive than the potential range in the presence of Br – (1.20 V vs RHE) and Cl – (1.39 V vs RHE), via a 1e – oxidation process in acidic thiourea solutions , forming Au(I)–TU complexes. In addition, the anodic oxidation of thiourea requires one electron per thiourea molecule to reversibly yield formamidine disulfide (FDS) .…”

Section: Introductionmentioning

confidence: 99%

Pit-Induced Electrochemical Layer Dissolution and Wave Propagation on an Au(111) Surface in an Acidic Thiourea Solution

Pan

Shan

et al. 2020

J. Phys. Chem. C

View full text Add to dashboard Cite

The mesoscopic evolution of the electrochemical dissolution of an Au(111) facet in acidic thiourea solutions was studied using in situ electrochemical atomic force microscopy (EC-AFM). At the open-circuit potential (OCP, 0.39 V vs RHE) of a gold bead electrode in 1.0 mM thiourea +0.1 M HClO4 solution, the Au(111) plane displays pit-induced layer dissolution, which subsequently transforms into a wave-type dissolution at a rate of 0.05 μm/min. The dissolution of the Au(111) is suppressed in the acidic thiourea solutions as the potential on the negative side of the OCP is varied from 0.37 to 0.28 V (vs RHE) but is promoted as the potential on the positive side of the OCP is varied from 0.42 to 0.58 V (vs RHE). As the applied potential becomes more positive than 0.58 V (vs RHE), the dissolution rate of the Au(111) plane becomes too fast, exceeding the scanning capacity of the EC-AFM. The Au-deposition, starting from 0.25 V (vs RHE) to lower potentials, could be observed by situ-EC-AFM. The reason for the formation of a wave-type dissolution of the Au(111) plane was illustrated through the bonding energy between the sulfur atom of thiourea and gold atoms located at different positions in the Au(111) facet. The dependence of the dissolution of the Au(111) plane on the applied potential in acidic thiourea media is clarified in this work, which provides a new understanding of the kinetics and mechanism for the leaching of gold by thiourea at the mesoscopic level.

show abstract

Anodic behavior of gold in acid thiourea solutions: A cyclic voltammetry and quartz microgravimetry study

Cited by 9 publications

References 8 publications

A Spectroelectrochemical Investigation of the Interaction of Gold with Cyano-Containing Ligands

A Spectroelectrochemical Investigation of the Interaction of Gold with Cyano-Containing Ligands

The microbalance determination of kinetic parameters of anodic dissolution of gold in thiocarbamide electrolytes in the presence of sulfide ions

Pit-Induced Electrochemical Layer Dissolution and Wave Propagation on an Au(111) Surface in an Acidic Thiourea Solution

Contact Info

Product

Resources

About