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Kitagaki BT, Pinto MR, Queiroz AC, Breitkreitz MC, Rossi F, Nagao R. Multivariate statistical analysis of chemical and electrochemical oscillators for an accurate frequency selection. Phys Chem Chem Phys 2019; 21:16423-16434. [PMID: 31144704 DOI: 10.1039/c9cp01998g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effect of experimental parameters on the frequency of chemical oscillators has been systematically studied since the first observations of clock reactions. The approach is mainly based on univariate changes in one specific parameter while others are kept constant. The frequency is then monitored and the effect of each parameter is discussed separately. This type of analysis, however, does not take into account the multiple interactions among the controllable parameters and the synergic responses on the oscillation frequency. We have carried out a multivariate statistical analysis of chemical (BZ-ferroin catalyzed reaction) and electrochemical (Cu/Cu2O cathodic deposition) oscillators and identified the contributions of the experimental parameters on frequency variations. The BZ reaction presented a strong dependence on the initial concentration of sodium bromate and temperature, resulting in a frequency increase. The concentration of malonic acid, the organic substrate, affects the system but with lower intensity compared with the combination of sodium bromate and temperature. On the other hand, the Cu/Cu2O electrochemical oscillator was shown to be less sensitive to changes in the temperature. The applied current density and pH were the two parameters which most perturbed the system. Interestingly, the frequency behaved nonmonotonically with a quadratic dependence. The multivariate analysis of both oscillators exhibited significant differences - while the homogenous oscillator displayed a linear dependence with the factors, the heterogeneous one revealed a more complex dependence with quadratic terms. Our results may contribute, for instance, in the synthesis of self-organized materials in which an accurate frequency selection is required and, depending on its value, different physicochemical properties are obtained.
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Affiliation(s)
- Bianca T Kitagaki
- Institute of Chemistry, University of Campinas, CEP 13083-970, Campinas, SP, Brazil.
| | - Maria R Pinto
- Institute of Chemistry, University of Campinas, CEP 13083-970, Campinas, SP, Brazil.
| | - Adriana C Queiroz
- Institute of Chemistry, University of Campinas, CEP 13083-970, Campinas, SP, Brazil. and Center for Innovation on New Energies, University of Campinas, CEP 13083-841, Campinas, SP, Brazil
| | - Márcia C Breitkreitz
- Institute of Chemistry, University of Campinas, CEP 13083-970, Campinas, SP, Brazil.
| | - Federico Rossi
- Department of Earth, Environmental and Physical Sciences - DEEP Sciences, University of Siena, Pian dei Mantellini 44, 53100, Siena, Italy
| | - Raphael Nagao
- Institute of Chemistry, University of Campinas, CEP 13083-970, Campinas, SP, Brazil. and Center for Innovation on New Energies, University of Campinas, CEP 13083-841, Campinas, SP, Brazil
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Electrochemical resonance under harmonic current perturbations and chaotic potential perturbations. J Solid State Electrochem 2015. [DOI: 10.1007/s10008-015-2794-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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The electro-oxidation of ethylene glycol on platinum over a wide pH range: oscillations and temperature effects. PLoS One 2013; 8:e75086. [PMID: 24058650 PMCID: PMC3776735 DOI: 10.1371/journal.pone.0075086] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 08/09/2013] [Indexed: 11/19/2022] Open
Abstract
We report a comprehensive study of the electro-oxidation of ethylene glycol (EG) on platinum with emphasis on the effects exerted by the electrolyte pH, the EG concentration, and temperature, under both regular and oscillatory conditions. We extracted and discussed parameters such as voltammetric activity, reaction orders (with respect to [EG]), oscillation's amplitude, frequency and waveform, and the evolution of the mean electrode potential at six pH values from 0 to 14. In addition, we obtained the apparent activation energies under several different conditions. Overall, we observed that increasing the electrolyte pH results in a discontinuous transition in most properties studied under both voltammetric and oscillatory regimes. As a relevant result in this direction, we found that the increase in the reaction order with pH is mediated by a minimum (~ 0) at pH = 12. Furthermore, the solution pH strongly affects all features investigated, c.f. the considerable increase in the oscillatory frequency and the decrease in the, oscillatory, activation energy as the pH increase. We suggest that adsorbed CO is probably the main surface-blocking species at low pH, and its absence at high pH is likely to be the main reason behind the differences observed. The size of the parameter region investigated and the amount of comparable parameters and properties presented in this study, as well as the discussion that followed illustrate the strategy of combining investigations under conventional and oscillatory regimes of electrocatalytic systems.
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Urvölgyi M, Gáspár V, Nagy T, Kiss IZ. Quantitative dynamical relationships for the effect of rotation rate on frequency and waveform of electrochemical oscillations. Chem Eng Sci 2012. [DOI: 10.1016/j.ces.2011.10.073] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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Ferreira GCA, Batista BC, Varela H. Experimental assessment of the sensitiveness of an electrochemical oscillator towards chemical perturbations. PLoS One 2012. [PMID: 23185559 PMCID: PMC3503998 DOI: 10.1371/journal.pone.0050145] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In this study we address the problem of the response of a (electro)chemical oscillator towards chemical perturbations of different magnitudes. The chemical perturbation was achieved by addition of distinct amounts of trifluoromethanesulfonate (TFMSA), a rather stable and non-specifically adsorbing anion, and the system under investigation was the methanol electro-oxidation reaction under both stationary and oscillatory regimes. Increasing the anion concentration resulted in a decrease in the reaction rates of methanol oxidation and a general decrease in the parameter window where oscillations occurred. Furthermore, the addition of TFMSA was found to decrease the induction period and the total duration of oscillations. The mechanism underlying these observations was derived mathematically and revealed that inhibition in the methanol oxidation through blockage of active sites was found to further accelerate the intrinsic non-stationarity of the unperturbed system. Altogether, the presented results are among the few concerning the experimental assessment of the sensitiveness of an oscillator towards chemical perturbations. The universal nature of the complex chemical oscillator investigated here might be used for reference when studying the dynamics of other less accessible perturbed networks of (bio)chemical reactions.
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Affiliation(s)
- Graziela C. A. Ferreira
- Institute of Chemistry of São Carlos, University of São Paulo, São Carlos, São Paulo, Brazil
| | - Bruno C. Batista
- Institute of Chemistry of São Carlos, University of São Paulo, São Carlos, São Paulo, Brazil
| | - Hamilton Varela
- Institute of Chemistry of São Carlos, University of São Paulo, São Carlos, São Paulo, Brazil
- Ertl Center for Electrochemistry and Catalysis, Gwangju Institute of Science and Technology, Gwangju, South Korea
- * E-mail:
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Mota A, Gonzalez ER, Eiswirth M. Kinetic insights over a PEMFC operating on stationary and oscillatory states. J Phys Chem A 2011; 115:13773-82. [PMID: 22017227 DOI: 10.1021/jp205341w] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Kinetic investigations in the oscillatory state have been carried out in order to shed light on the interplay between the complex kinetics exhibited by a proton exchange membrane fuel cell fed with poisoned H(2) (108 ppm of CO) and the other in serie process. The apparent activation energy (E(a)) in the stationary state was investigated in order to clarify the E(a) observed in the oscillatory state. The apparent activation energy in the stationary state, under potentiostatic control, rendered (a) E(a) ≈ 50-60 kJ mol(-1) over 0.8 V < E < 0.6 V and (b) E(a) ≈ 10 kJ mol(-1) at E = 0.3 V. The former is related to the H(2) adsorption in the vacancies of the surface poisoned by CO and the latter is correlated to the process of proton conductivity in the membrane. The dependence of the period-one oscillations on the temperature yielded a genuine Arrhenius dependence with two E(a) values: (a) E(a) around 70 kJ mol(-1), at high temperatures, and (b) E(a) around 10-15 kJ mol(-1), at lower temperatures. The latter E(a) indicates the presence of protonic mass transport coupled to the essential oscillatory mechanism. These insights point in the right direction to predict spatial couplings between anode and cathode as having the highest strength as well as to speculate the most likely candidates to promote spatial inhomogeneities.
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Affiliation(s)
- Andressa Mota
- Instituto de Química de São Carlos, Av. Trab. Sancarlense 400, CEP 13560-970, São Carlos-SP, Brazil.
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Cioffi AG, Martin RS, Kiss IZ. Electrochemical Oscillations of Nickel Electrodissolution in an Epoxy-Based Microchip Flow Cell. J Electroanal Chem (Lausanne) 2011; 659:92-100. [PMID: 21822407 PMCID: PMC3150514 DOI: 10.1016/j.jelechem.2011.05.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We investigate the nonlinear dynamics of transpassive electrodissolution of nickel in sulfuric acid in an epoxy-based microchip flow cell. We observed bistability, smooth, relaxation, and period-2 waveform current oscillations with external resistance attached to the electrode in the microfabricated electrochemical cell with 0.05 mm diameter Ni wire under potentiostatic control. Experiments with 1mm × 0.1 mm Ni electrode show spontaneous oscillations without attached external resistance; similar surface area electrode in macrocell does not exhibit spontaneous oscillations. Combined experimental and numerical studies show that spontaneous oscillation with the on-chip fabricated electrochemical cell occurs because of the unusually large ohmic potential drop due to the constrained current in the narrow flow channel. This large IR potential drop is expected to have an important role in destabilizing negative differential resistance electrochemical (e.g., metal dissolution and electrocatalytic) systems in on-chip integrated microfludic flow cells. The proposed experimental setup can be extendend to multi-electrode configurations; the epoxy-based substrate procedure thus holds promise in electroanalytical applications that require collector-generator multi-electrodes wires with various electrode sizes, compositions, and spacings as well as controlled flow conditions.
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Affiliation(s)
- Alexander G. Cioffi
- Saint Louis University, Department of Chemistry, 3501 Laclede Ave., St. Louis, MO 63103
| | - R. Scott Martin
- Saint Louis University, Department of Chemistry, 3501 Laclede Ave., St. Louis, MO 63103
| | - István Z. Kiss
- Saint Louis University, Department of Chemistry, 3501 Laclede Ave., St. Louis, MO 63103
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Wickramasinghe M, Kiss IZ. Effect of temperature on precision of chaotic oscillations in nickel electrodissolution. CHAOS (WOODBURY, N.Y.) 2010; 20:023125. [PMID: 20590321 DOI: 10.1063/1.3439209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
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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Affiliation(s)
- Mahesh Wickramasinghe
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave., St. Louis, Missouri 63103, USA
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Sitta E, Nascimento MA, Varela H. Complex kinetics, high frequency oscillations and temperature compensation in the electro-oxidation of ethylene glycol on platinum. Phys Chem Chem Phys 2010; 12:15195-206. [PMID: 20661518 DOI: 10.1039/c002574g] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Elton Sitta
- Instituto de Química de São Carlos, Universidade de São Paulo C.P. 780, CEP 13560-970, São Carlos, SP, Brazil
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