scholarly journals The Interface is a Tunable Dimension in Electricity-Driven Organic Synthesis

2021 ◽  
Author(s):  
Anna Wuttig ◽  
Dean Toste
Keyword(s):  
Organic Synthesis ◽  
Predictive Control ◽  
Electrode Surface ◽  
Electrochemical Process ◽  
Synthetic Method ◽  
Reaction Selectivity ◽  
Electrochemical Systems ◽  
Electrochemical Processes ◽  
Co2 Electroreduction ◽  
Molecular Complexity

Predictive control over the selectivity outcome of an organic synthetic method is an essential hallmark of reaction success. Electricity-driven synthesis offers a reemerging approach to facilitate the design of reaction sequences towards increased molecular complexity. In addition to the desirable sustainability features of electroorganic processes, the inherent interfacial nature of electrochemical systems present unique opportunities to tune reaction selectivity. To illustrate this feature, we outline examples of mechanism-guided interfacial control over CO2 electroreduction selectivity, a well-studied and instructive electrochemical process with multiple reduction products that are thermodynamically accessible. These studies reveal how controlled proton delivery to the electrode surface and substrate electroadsorption with the electrode dictate reaction selectivity. We describe and compare simple, yet salient, examples from the electroorganic literature, where we postulate that similar effects predominate the observed reactivity. This perspective highlights how the interface serves as a tunable dimension in electrochemical processes, delineating unique tools to study, manipulate, and achieve reaction selectivity in electricity-driven organic synthesis.

scholarly journals (ECS 235th) Estimation of the Onset of Mass Transfer Limitations in Pulsed Electrochemical Processes

2019 ◽  
Author(s):  
Brian Skinn
Keyword(s):  
Mass Transfer ◽  
Current Distribution ◽  
Current Density ◽  
Electrode Surface ◽  
Electrochemical Process ◽  
Transition Time ◽  
Workpiece Surface ◽  
Electrochemical Processes ◽  
Simplifying Assumptions ◽  
Transition Times

The contributions of the physical phenomena governing the distribution of current across an electrode in an electrochemical process are conventionally categorized as primary, secondary, and/or tertiary current distribution effects, which respectively embody geometric/ohmic, kinetic polarization, and concentration polarization effects. On virtually all non-trivial workpieces of interest to industrial electrochemical practice, it is important to be able to control the areas affected by the process; viz., preferentially adding or removing material to some regions over others. Two of the most significant phenomena contributing to the tertiary current distribution in electrochemical processes are depletion (for electrodeposition) and saturation (for electrodissolution) of the active soluble metal species at the workpiece surface. Both of these phenomena lead to mass-transfer limitations: taking electrodissolution as an example, if material is being dissolved at a particular point on the electrode surface at a rate greater than diffusion can carry the products away from the surface, then mass-transfer limitations will result. The tertiary current distribution effects arising from these limitations will tend to disfavor further increases in the local electrodissolution current density at that point, thus shifting the current density distribution to other locations on the workpiece surface, to other reactions at the same location, or both. Thus, exerting control over these tertiary current distribution effects can be highly valuable for developing an efficient and accurate electrochemical process.An interesting feature of these mass-transfer-limiting phenomena is that they are almost entirely inactive for a short time (generally < 1 s for processes of practical interest) after the electrical voltage is applied, even if the applied current density is sufficiently high that significant mass transfer limitations will result after this initial interval. Thus, it follows that pulsing the applied potential/current at sufficiently high frequencies has the potential to enable significant control of these tertiary current distribution effects, by allowing the physicochemical conditions contributing to mass-transfer limitations at the electrode surface to “relax” while the potential is turned off. For the purposes of electrochemical process optimization, the ability to estimate the maximum concentration of dissolved species at the electrode surface for a given system and applied waveform would provide guidance as to whether and when a particular mode of mass-transfer limitation is likely to be active. In particular, evaluation of the “transition time,” the value of the waveform on-time above which mass-transfer limitations become appreciable, is of significant practical interest.Methods for transition time estimation based on linearized approximation of the boundary-layer concentration dynamics under a number of simplifying assumptions are available in the literature; e.g., Ref. [1]. However, the transition times calculated using these methods were found to deviate from COMSOL Multiphysics® simulation results by anywhere between –80% to +2780%, depending on the form of the estimation used and the particular waveform under consideration. This talk summarizes a method developed to provide appreciably more accurate predictions of transition times, under a similar set of simplifying assumptions as in Ref. 1. Separate on-time and off-time analytical solutions of the time-dependent steady-periodic mass transport behavior in a one-dimensional boundary layer were developed via the ‘finite Fourier transform’ (FFT) technique [[2]] and used to generate transition time estimates. Optimal values of the FFT model parameters were separately identified for fifty-three pairs of two pulsed-waveform timing parameters, period and duty cycle, spanning substantially the entire parameter space of practical industrial relevance. When compared to COMSOL® simulation results, the deviation of the transition time predictions (equivalently, predictions of the maximum surface concentration, in the electrodissolution paradigm of the model) was within 9% for all of the examined sets of timing parameters, with most deviating less than 5%. This FFT method thus provides a highly accurate method for estimation of transition times, within the approximations made in constructing the model.References[[1]] Ibl, N. “Some Theoretical Aspects of Pulse Electrolysis.” Surface Technology 10: 81-104 (1980).[[2]] Deen, W.M. “Analysis of Transport Phenomena,” 2nd ed., Ch. 5. New York: Oxford University Press, 2012.

Promoting CO2 electroreduction on CuO nanowires with a hydrophobic Nafion overlayer

Nanoscale ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 3588-3593
Author(s):  
Mang Wang ◽  
Lili Wan ◽  
Jingshan Luo
Keyword(s):  
Hydrogen Evolution ◽  
Electrode Surface ◽  
Cuo Nanowires ◽  
Co2 Electroreduction ◽  
Cuo Nanowire ◽  
Enhanced Selectivity

A hydrophobic electrode surface was constructed by modifying the CuO nanowire electrode with a thick Nafion overlayer, which exhibited enhanced selectivity toward the CO2 electroreduction reaction and suppressed hydrogen evolution activity.

scholarly journals A Comparative Electrochemical-Ozone Treatment for Removal of Phenolphthalein

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
V. M. García-Orozco ◽  
C. E. Barrera-Díaz ◽  
G. Roa-Morales ◽  
Ivonne Linares-Hernández
Keyword(s):  
Electrochemical Treatment ◽  
Electrochemical Process ◽  
Ozone Treatment ◽  
Acidic Ph ◽  
Alkaline Ph ◽  
Diamond Electrodes ◽  
Boron Doped Diamond ◽  
Boron Doped ◽  
Electrochemical Processes ◽  
Density Values

The degradation of aqueous solutions containing phenolphthalein was carried out using ozone and electrochemical processes; the two different treatments were performed for 60 min at pH 3, pH 7, and pH 9. The electrochemical oxidation using boron-doped diamond electrodes processes was carried out using three current density values: 3.11 mA·cm−2, 6.22 mA·cm−2, and 9.33 mA·cm−2, whereas the ozone dose was constantly supplied at 5±0.5 mgL−1. An optimal degradation condition for the ozonation treatment is at alkaline pH, while the electrochemical treatment works better at acidic pH. The electrochemical process is twice better compared with ozonation.

Control of disinfection and halogenated disinfection byproducts by the electrochemical process

2007 ◽  
Vol 55 (12) ◽  
pp. 213-219 ◽  
Author(s):  
Y.J. Jung ◽  
B.S. Oh ◽  
J.W. Kang ◽  
M.A. Page ◽  
M.J. Phillips ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Disinfection Byproducts ◽  
Electrochemical Process ◽  
Free Chlorine ◽  
Haloacetic Acids ◽  
Oh Radicals ◽  
Inactivation Kinetic ◽  
E Coli ◽  
Electrochemical Processes

The aim of this study was to investigate some aspects of the performance of electrochemical process as an alternative disinfection strategy, while minimising DBPs, for water purification. The study of electrochemical processes has shown free chlorine to be produced, but smaller amounts of stronger oxidants, such as ozone, hydrogen peroxide and OH radicals (•OH), were also generated. The formation of mixed oxidants increased with increasing electric conductivity, but was limited at conductivities greater than 0.6 mS/cm. Using several microorganisms, such as E. coli and MS2 bacteriophage, inactivation kinetic studies were performed. With the exception of free chlorine, the role of mixed oxidants, especially OH radicals, was investigated for enhancement of the inactivation rate. Additionally, the formation and reduction of DBPs was studied by monitoring the concentration of haloacetic acids (HAAs) during the process.

scholarly journals Ionization of Water as an Effect of Quantum Delocalization at Aqueous Electrode Interfaces

2020 ◽  
Author(s):  
Jinggang Lan ◽  
Vladimir V. Rybkin ◽  
Marcella Iannuzzi
Keyword(s):  
Molecular Dynamics ◽  
Path Integral ◽  
Electrode Surface ◽  
Metal Electrode ◽  
Ab Initio Molecular Dynamics ◽  
Water Dissociation ◽  
Statistical Sampling ◽  
Electrochemical Processes ◽  
Nuclear Quantum Effects ◽  
Ionization Of Water

<div><div><div><p>The enhanced probability of water dissociation at the aqueous electrode interfaces is predicted by path-integral ab initio molecular dynamics. The ionization process is observed at the aqueous platinum interface when nuclear quantum effects are introduced in the statistical sampling, while minor effects have been observed at the gold interface. We characterize the dissociation mechanism and the dynamics of the formed water ions. In spite of the fact that the concentration and lifetime of the ions might be challenging to be experimentally detectable, they may serve as a guide to future experiments. Our observation might have a significant impact on the understanding of electrochemical processes occurring at the metal electrode surface.</p></div></div></div>

scholarly journals ELECTROCHEMICAL BEHAVIOR OF SILVER IN A SULPHURIC ACID SOLUTION

2020 ◽  
Vol 6 (444) ◽  
pp. 30-37
Author(s):  
A. B. Baeshov ◽  
◽  
E. Zh. Tuleshova ◽  
A. K. Baeshova ◽  
M. A. Ozler ◽  
...  
Keyword(s):  
Alternating Current ◽  
Sulphuric Acid Solution ◽  
Electrochemical Process ◽  
Silver Electrode ◽  
Half Period ◽  
Distinctive Features ◽  
Titanium Electrode ◽  
Electrochemical Processes ◽  
Electrochemical Technology ◽  
Rate Of Dissolution

In recent years, alternating current has been widely used in various fields of chemical and electrochemical technology. When a symmetric alternating current passes through an electrochemical cell, in principle there should be no visible changes, since the product restored to the cathode half-period should be oxidized back to the anodic half-period. However, depending on the conditions of electrolysis, electrode material, etc. a purposeful course of the electrochemical process is possible. The paper shows the distinctive features of electrochemical processes occurring on a silver electrode during electrolysis by industrial alternating current in a solution of sulfuric acid by the method of rational mathematical planning. The optimal conditions for the dissolution of silver are determined by studying the effect of current density at the electrodes, the concentration and temperature of the electrolyte, the duration of the electrolysis and the frequency of the alternating current. It is shown that when polarized with an alternating current of silver in a pair with a titanium electrode, the process of passivation of the silver electrode is eliminated, and the rate of dissolution of the metal increases.

(Invited) Estimation of the Onset of Mass Transfer Limitations in Pulsed Electrochemical Processes

2019 ◽  
Vol MA2019-01 (20) ◽  
pp. 1100-1100
Author(s):  
Brian Skinn
Keyword(s):  
Mass Transfer ◽  
Current Distribution ◽  
Current Density ◽  
Electrode Surface ◽  
Practical Interest ◽  
Electrochemical Process ◽  
Transition Time ◽  
Workpiece Surface ◽  
Simplifying Assumptions ◽  
Transition Times

The contributions of the physical phenomena governing the distribution of current across an electrode in an electrochemical process are conventionally categorized as primary, secondary, and/or tertiary current distribution effects, which respectively embody geometric/ohmic, kinetic polarization, and concentration polarization effects. On virtually all non-trivial workpieces of interest to industrial electrochemical practice, it is important to be able to control the areas affected by the process; viz., preferentially adding or removing material to some regions over others. Two of the most significant phenomena contributing to the tertiary current distribution in electrochemical processes are depletion (for electrodeposition) and saturation (for electrodissolution) of the active soluble metal species at the workpiece surface. Both of these phenomena lead to mass-transfer limitations: taking electrodissolution as an example, if material is being dissolved at a particular point on the electrode surface at a rate greater than diffusion can carry the products away from the surface, then mass-transfer limitations will result. The tertiary current distribution effects arising from these limitations will tend to disfavor further increases in the local electrodissolution current density at that point, thus shifting the current density distribution to other locations on the workpiece surface, to other reactions at the same location, or both. Thus, exerting control over these tertiary current distribution effects can be highly valuable for developing an efficient and accurate electrochemical process. An interesting feature of these mass-transfer-limiting phenomena is that they are almost entirely inactive for a short time (generally < 1 s for processes of practical interest) after the electrical voltage is applied, even if the applied current density is sufficiently high that significant mass transfer limitations will result after this initial interval. Thus, it follows that pulsing the applied potential/current at sufficiently high frequencies has the potential to enable significant control of these tertiary current distribution effects, by allowing the physicochemical conditions contributing to mass-transfer limitations at the electrode surface to “relax” while the potential is turned off. This “relaxation” behavior is schematized in Figure 1 for a generic pulse-electrodissolution process under steady-periodic conditions, where the orange and blue traces represent the concentration profiles at the end of the on-time and off-time, respectively, under conditions where no mass-transfer limitations are active at any point in time. For the purposes of electrochemical process optimization, the ability to estimate the maximum concentration of dissolved species at the electrode surface for a given system and applied waveform would provide guidance as to whether and when a particular mode of mass-transfer limitation is likely to be active. In particular, evaluation of the “transition time,” the value of the waveform on-time above which mass-transfer limitations become appreciable, is of significant practical interest. Methods for transition time estimation based on linearized approximation of the boundary-layer concentration dynamics under a number of simplifying assumptions are available in the literature; e.g., Ref. [1]. However, the transition times calculated using these methods were found to deviate from COMSOL Multiphysics® simulation results by anywhere between –80% to +2780%, depending on the form of the estimation used and the particular waveform under consideration. This talk summarizes a method developed to provide appreciably more accurate predictions of transition times, under a similar set of simplifying assumptions as in Ref. 1. Separate on-time and off-time analytical solutions of the time-dependent steady-periodic mass transport behavior in a one-dimensional boundary layer were developed via the ‘finite Fourier transform’ (FFT) technique [[2]] and used to generate transition time estimates. Optimal values of the FFT model parameters were separately identified for fifty-three pairs of two pulsed-waveform timing parameters, period and duty cycle, spanning substantially the entire parameter space of practical industrial relevance. When compared to COMSOL® simulation results, the deviation of the transition time predictions (equivalently, predictions of the maximum surface concentration, in the electrodissolution paradigm of the model) was within 9% for all of the examined sets of timing parameters, with most deviating less than 5%. This FFT method thus provides a highly accurate method for estimation of transition times, within the approximations made in constructing the model. References [[1]] Ibl, N. “Some Theoretical Aspects of Pulse Electrolysis.” Surface Technology 10: 81-104 (1980). [[2]] Deen, W.M. “Analysis of Transport Phenomena,” 2nd ed., Ch. 5. New York: Oxford University Press, 2012. Figure 1

Electroorganic Synthesis Engineering

2001 ◽  
Author(s):  
L. K. Doraiswamy
Keyword(s):  
Organic Synthesis ◽  
Process Analysis ◽  
Inorganic Compounds ◽  
Electrochemical Techniques ◽  
Electrochemical Process ◽  
Transport Processes ◽  
Reaction Engineering ◽  
Electroorganic Synthesis ◽  
Limited Application ◽  
The Subject

Historically, electrochemical processes have been limited to the production of inorganic compounds, and commercial processes based on electroorganic synthesis have found only limited application. It appeared to be an “odious truth” (Fry, 1972) that electrochemical techniques were ignored in organic synthesis. But the past 25 years have witnessed the introduction of a fairly large number of new electroorganic processes with attendant advances in electrochemical process analysis. The most remarkable has been Monsanto’s highly successful electrochemical route for the production of adiponitrile. A particularly notable advance is the electrosynthesis of fine chemicals and natural products. Combinations of electrosynthesis with other strategies of rate or selectivity enhancement such as catalysis by PTC and by enzymes (Chapters 19 and 20) are also adding exciting possibilities to organic synthesis. Simultaneously, fundamental understanding of the principles of organic electrochemistry, electrode kinetics, and transport processes in electrochemical systems has grown rapidly in the last decade. A number of books and reviews have appeared on electroorganic chemistry during this period, for example, Eberson and Schafer (1971), Fry (1972), Beck (1974), Perry and Chilton (1976), Rifi and Covitz (1975, 1980), Weinberg (1974, 1990), Swann and Alkire (1980), Kyriacou (1981), Fletcher (1982), Baizer and Lund (1983), Baizer (1973, 1984), Shono (1984), Fletcher and Walsh (1990), Little and Weinberg (1991), Bowden (1997), Bockris (1998), Hamann (1998). This period also saw the emergence of electrochemical reaction engineering as a distinct discipline of chemical reaction engineering, as evidenced by a number of books and reviews on the subject, for example, Picket (1979), Udupa (1979), Danly (1980, 1984), Alkire and Beck (1981), Weinberg et al. (1982), Alkire and Chin (1983), Fahidy (1985), Mine (1985), Goodridge et al. (1986), Rousar et al. (1986), Heitz and Krysa (1986), Ismail (1989), Scott (1991), Prentice (1991), Goodridge and Scott (1995). Electroorganic synthesis offers opportunities for performing many of the conventional organic reactions at controlled rates and greater product selectivities without the addition of any catalyst. The processes almost always employ milder conditions and are characterized by greatly reduced air and water pollution. Further, there are a number of syntheses that can only be carried out electrochemically, such as the Kolbe synthesis and electrochemical perfluorination.

New applications of organofluorine reagents in organic synthesis. III. A convenient synthetic method for acetylenic ethers and thioethers

1978 ◽  
Vol 19 (34) ◽  
pp. 3103-3106 ◽  
Author(s):  
Kiyoshi Tanaka ◽  
Shuichi Shiraishi ◽  
Takeshi Nakai ◽  
Nobuo Ishikawa
Keyword(s):  
Organic Synthesis ◽  
Synthetic Method ◽  
New Applications
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