Dynamic Complexity in the Electrochemical Oxidation of Thiourea

Feng, Jiu‐Ju; Gao, Qingyu; Lv, Xiaoli; Epstein, Irving R.

doi:10.1021/jp802002k

Cited by 13 publications

(15 citation statements)

References 29 publications

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“…With the excess amount of hydrogen peroxide, the final oxidation product, sulfate, was identified by adding BaCl 2 solution to the acidified reaction solution. Figure 5 Through HPLC-MS analysis of species in the oxidation of FDS by hydrogen peroxide, urea (NH 2 ) 2 CO was detected ([M + H] + = 61.2), consistent with the previous study [19]. The influence of [H 2 O 2 ] 0 /[FDS] 0 on the reaction rate con- n , the expression of k can be converted to k = k h + k 1 in which k 1 is the pseudo-first order apparent rate-constant for FDS oxidation.…”

Section: Oxidation Kinetics Of Fdssupporting

confidence: 90%

“…Investigations during the past couple of decades indicated that the oxidation processes displayed extremely rich nonlinear phenomena including autocatalysis, autoinhibition, bistability, oligooscillations, oscillations, birhythmicity, chaos, and spatiotemporal pattern [110]. When TU was oxidized on a platinum electrode, period-doubling bifurcation, two-and threefrequency quasi-periodic and other complex oscillatory phenomena can be observed [18,19]. To uncover the core oscillatory mechanism underlying such phenomena, extensive efforts [5,6,10,20] were devoted to the study of these reactions, indicating that formamidine disulfide (FDS, H 2 N(=NH)CS-SC(=NH)NH 2 ) is an important intermediate in the oxidation of TU.…”

Section: Introductionmentioning

confidence: 99%

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Kinetic study on hydrolysis and oxidation of formamidine disulfide in acidic solutions

Feng

et al. 2011

Sci. China Chem.

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Hydrolysis and oxidation of formamidine disulfide in acidic medium were investigated using high-performance liquid chromatography (HPLC) and mass spectrometry (MS) at 25 °C. By controlling the slow reaction rate and choosing appropriate mobile phase, HPLC provides the unique advantages over other methods (UV-Vis, chemical separation) in species tracking and kinetic study. In addition to thiourea and formamidine sulfinic acid, two unreported products were also detected in the hydrolysis reaction. Mass spectrometry measurement indicates these two products to be formamidine sulfenic acid and thiocyanogen with mass weights of 92.28 and 116.36, respectively. In the oxidation of formamidine disulfide by hydrogen peroxide, besides thiourea, formamidine sulfenic acid, formamidine sulfinic acid, thiocyanogen and urea, formamidine sulfonic acid and sulfate could be detected. The oxidation reaction was found to be first order in both formamidine disulfide and hydrogen peroxide. The rate constants of hydrolysis and oxidation reactions were determined in the pH range of 1.5-3.0. It was found both rate constants are increased with the increasing of pH. Experimental curves of different species can be effectively simulated via a mechanism scheme for formamidine disulfide oxidation, including hydrolysis equilibrium of formamidine disulfide and irreversible hydrolysis of formamidine sulfenic acid.formamidine disulfide, hydrolysis, oxidation, HPLC-MS

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Section: Oxidation Kinetics Of Fdssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Kinetic study on hydrolysis and oxidation of formamidine disulfide in acidic solutions

Feng

et al. 2011

Sci. China Chem.

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“…25 In the oscillatory electrochemical urea system two-frequency quasiperiodic oscillation is transformed to three-frequency oscillations with increase in temperature. 35 Our experiments show that the phase coherent chaotic dissolution at low temperature becomes non-phasecoherent at elevated temperatures. The synchronization properties of phase coherent chaotic oscillations are quite different from those of non-phase-coherent oscillators; 12,16 therefore, nickel dissolution could be used as an experimental test bed for studying different, phase diffusion dependent routes to synchrony.…”

Section: Discussionmentioning

confidence: 64%

Effect of temperature on precision of chaotic oscillations in nickel electrodissolution

Wickramasinghe

Kiss

2010

Chaos: An Interdisciplinary Journal of Nonlinear Science

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We investigate the effects of temperature on complexity features of chaotic electrochemical oscillations using the anodic electrodissolution of nickel in sulfuric acid. The precision of the "period" of chaotic oscillation is characterized by phase diffusion coefficient (D). It is shown that reduced phase diffusion coefficient (D/frequency) exhibits Arrhenius-type dependency on temperature with apparent activation energy of 108 kJ/mol. The reduced Lyapunov exponent of the attractor exhibits no considerable dependency on temperature. These results suggest that the precision of electrochemical oscillations deteriorates with increase in temperature and the variation of phase diffusion coefficient does not necessarily correlate with that of Lyapunov exponent. Modeling studies qualitatively simulate the behavior observed in the experiments: the precision of oscillations in the chaotic Ni dissolution model can be tuned by changes of a time scale parameter of an essential variable, which is responsible for the development of chaotic behavior.

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“…This was achieved with a core driven software PAR 283 Potentiostat/Galvanostat (PG/GS) and a Z-plot driven solartron instrument [3]. Cleaning of the electrodes was done prior to the experiment, for the purpose of revealing the surface of the electrodes which might have been covered by impurities, and conditioned them for the experiment as reported by Feng et al, [10]. The 0.5 M HCl was prepared, and the electrodes were immersed in the diluted solution.…”

Section: Materials and Instrumentationsmentioning

confidence: 99%

Electrochemical Study of Redox Reaction of Various Gold III Chloride Concentrations in Acidic Solution

Ayeni¹,

Alam²,

Kipouros³

2018

MSCE

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The redox reaction of gold III chloride in acid solutions has been electrochemically investigated using a cyclic voltammetry technique. This paper emphasizes the current and potential sites at which gold III chloride is reduced in hydrochloric acid that is vital to electrochemical evaluation of gold recovery. The solutions were prepared by reacting HCl with AuCl 3 in various concentrations thus 30 and 60 mg/L AuCl 3 in 0.1 and 0.5 M HCl, respectively. Solutions of 0.1 and 0.5 M HCl containing 0, 30 and 60 mg/L AuCl 3 , respectively were tested for possible reduction and oxidation reactions by cyclic voltammogram experiment using a glassy carbon, a saturated calomel and a platinum wire mesh as working, reference and counter electrodes, respectively. The results showed no peak in the case of the absence of AuCl 3 in the solutions, but appreciable cathodic and anodic peaks for the reduction and oxidation of various concentrations of AuCl 3 in acid solutions. The reaction between AuCl 3 and HCl was found to be reversible because the ratio of oxidation peak current and reduction peak current was 1. The concentration of 4 AuCl − on the surface of the working electrode at the reduction site for each AuCl 3 concentration using Nernst equation was 1.22 × 10 9 ppm and 2.44 × 10 9 ppm. The reduction potentials were independent of concentration, while the current was highly dependent of concentration.

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Dynamic Complexity in the Electrochemical Oxidation of Thiourea

Cited by 13 publications

References 29 publications

Kinetic study on hydrolysis and oxidation of formamidine disulfide in acidic solutions

Kinetic study on hydrolysis and oxidation of formamidine disulfide in acidic solutions

Effect of temperature on precision of chaotic oscillations in nickel electrodissolution

Electrochemical Study of Redox Reaction of Various Gold III Chloride Concentrations in Acidic Solution

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