Constant Potential Conditions Research Articles

Constant inner potential DFT for modelling electrochemical systems under constant potential and bias

Electrochemical systems play a decisive role in, e.g. clean energy conversion but understanding their complex chemistry remains an outstanding challenge. Constant potential and grand canonical ensemble (GCE) simulations are indispensable for unraveling the properties of electrochemical processes as a function of the electrode potential. Currently, GCE calculations performed at the density functional theory (DFT) level require fixing the Fermi level within the simulation cell. Here, we illustrate that this method is inadequate when modeling outer sphere reactions and a biased two-electrode cell. For these systems, the Fermi level obtained from DFT calculations does not accurately present the experimentally controlled electrode potential or describe the thermodynamic independent variable in GCE-DFT. To address this limitation, we developed and implemented a constant inner potential (CIP) method offering a more robust and general approach to conducting GCE-DFT simulations of electrochemical systems under constant potential or bias conditions. The primary advantage of CIP is that it uses the local electrode inner potential as the thermodynamic parameter for the electrode potential, as opposed to the global Fermi level. Through numerical and analytical studies, we demonstrate that the CIP and Fermi level GCE-DFT approaches are equivalent for metallic electrodes and inner-sphere reactions. However, CIP proves to be more versatile, as it can be applied to outer-sphere and two-electrode systems, addressing the limitations of the constant Fermi-level approach in these scenarios. Altogether, the CIP approach stands out as a general and efficient GCE-DFT method simulating electrochemical interfaces from first principles.

Molecular Simulation of Nafion Swelling in the Cathode Catalyst Layer of Polymer Electrolyte Fuel Cells

As the world moves towards carbon neutrality, polymer electrolyte fuel cells (PEFCs) have emerged as a vital technology in recent years. The cathode catalyst layer of PEFCs is characterized by its porous structure, which promotes the production of water molecules from oxygen and protons through chemical reactions. The ionomer thin films, predominantly composed of Nafion, are critical in regulating the transport and mobility of molecules and ions in the cathode catalyst layer. Sulfonic groups in the side chains of Nafion enable accumulation of water molecules, causing the ionomer thin films to swell.Previous studies have examined the swelling of Nafion under wet conditions[1][2]. However, precise swelling mechanisms remain unclear. While privious research has analyzed the relationship between relative humidity and the amount of water within bulk Nafion samples[3], the swelling behavior in films with thickness of several nanometers differs significantly, necessitating further investigation[4]. This study therefore investigates the swelling mechanisms and the properties of ionomer thin films used in the cathode catalyst layer of PEFCs. This study aims to establish guidelines for designing the molecular structures of ionomers by elucidating the mechanisms underlying ionomer swelling in the cathode catalyst layer. Grand canonical Monte Carlo (GCMC) simulations and molecular dynamics (MD) simulations were employed to reproduce swelling in Nafion thin films and examine the impact of Nafion's structure on water content and swelling. These molecular simulation techniques enable the elucidation of the influence exerted by polymer structure on water content and swelling at the molecular scale.In this study, we firstly created a simulation model of a Nafion system using LAMMPS[5], the DREIDING Force Field[6], and Mulliken charges[7] in which parameter settings were referred from literature values[8]. The Nafion system contains 10 Nafion molecules with a degree of polymerization of 10, water molecules, and 100 oxonium ions for electrical neutrality. The density of 1.9 g/cm3 achieved during simulations closely agrees with literature values[8].To reproduce Nafion swelling under humid conditions, GCMC simulations and MD simulations were employed. The rationale behind utilizing GCMC simulations lies in the fact that they enable the insertion of water molecules into the Nafion system under constant chemical potential conditions, thereby inducing Nafion swelling. Subsequent to the GCMC simulations, MD simulations were performed under the NPT ensemble, which facilitated the system to reach equilibrium. This alternating cycle of GCMC and MD simulations is repeated to realize the final swelling state. Preliminary results indicate lower water content values than those experimentally measured under similar conditions. Possible causes include inadequate force field parameters that lead to polymer morphology different from the actual Nafion structure.Future work will explore the causes of these discrepancies and examine the effects of Nafion's structure on water content and swelling under various conditions. This will involve testing alternative force field parameters and initial structures to better represent the molecular-level structure of ionomer thin films on carbon support particles in the cathode catalyst. Additionally, we will investigate how different relative humidity conditions, temperatures, and ionomer compositions influence swelling behavior, which could provide insights into optimizing PEFCs performance under various operating environments.[1] G. C. Abuin et al., J. Membr. Sci. 428, 507 (2013).[2] J. Catalano et al., Int. J. Hydrog. Energy 37, 6308 (2012).[3] T. A. Zawadzinski et al., J. Electrochem. Soc. 140, 1981 (1993).[4] M. A. Modestino et al., Macromolecules 46, 867 (2013).[5] A. P. Thompson et al., Comp. Phys. Comm. 271, 10817 (2022).[6] S. L. Mayo et al., J. Phys. Chem. 94, 8897 (1990).[7] S. S. Jang et al., J. Phys. Chem. B 108, 3149 (2004).[8] Y. Kurihara et al., J. Power Sources 414, 263 (2019).Fig. 1 An ionomer model composed of Nafion molecules, oxonium ions, and water molecules. The red and white spheres represent oxygen and hydrogen atoms making up water molecules. The size of the water molecules is emphasized for clarity. Figure 1

Theoretical Study on the Mechanism of CO* Electrochemical Reduction on Cu(111) under Constant Potential

In order to understand the mechanism of the electrochemical reduction of CO* on Cu(111), which competitively generates two intermediates, CHO* and COH*, we performed a first principles calculation on these two electrocatalytic reactions, including the solvent effect and imposing a constant potential. The transition states of the two reactions under constant potential conditions were located by the electrochemical nudged elastic band (eNEB) method and the charge effect in the two reactions was elucidated by charge correction in the constant potential model and Bader charge analysis. It was found that the two reactions have different potential dependencies and involve different degrees of partial charge transfer. In addition, we confirmed that the COH* reaction pathway exists only in a certain potential range when using the implicit solvent model.

Ease of Electrochemical Arsenate Dissolution from FeAsO4 Microparticles during Alkaline Oxygen Evolution Reaction.

Transition metal-based ABO4-type materials have now been paid significant attention due to their excellent electrochemical activity. However, a detailed study to understand the active species and its electro-evolution pathway is not traditionally performed. Herein, FeAsO4, a bimetallic ABO4-type oxide, has been prepared solvothermally. In-depth microscopic and spectroscopic studies showed that the as-synthesized cocoon-like FeAsO4 microparticles consist of several small individual nanocrystals with a mixture of monoclinic and triclinic phases. While depositing FeAsO4 on three-dimensional nickel foam (NF), it can show oxygen evolution reaction (OER) in a moderate operating potential. During the electrochemical activation of the FeAsO4/NF anode through cyclic voltammetric (CV) cycles prior to the OER study, an exponential increment in the current density (j) was observed. An ex situ Raman study with the electrode along with field emission scanning electron microscopy imaging showed that the pronounced OER activity with increasing number of CV cycles is associated with a rigorous morphological and chemical change, which is followed by [AsO4]3- leaching from FeAsO4. A chronoamperometric study and subsequent spectro- and microscopic analyses of the isolated sample from the electrode show an amorphous γ-FeO(OH) formation at the constant potential condition. The in situ formation of FeO(OH)ED (ED indicates electrochemically derived) shows better activity compared to pristine FeAsO4 and independently prepared FeO(OH). Tafel, impedance spectroscopic study, and determination of electrochemical surface area have inferred that the in situ formed FeO(OH)ED shows better electro-kinetics and possesses higher surface active sites compared to its parent FeAsO4. In this study, the electrochemical activity of FeAsO4 has been correlated with its structural integrity and unravels its electro-activation pathway by characterizing the active species for OER.

One-dimensional physical model for complementary electrochromic device

Eletrochromic devices are electrochemical systems that can undergo the optical modulation in response to an applied electrical stimulus. In order to investigate the electrochromic (EC) process mechanism and predict the electrochromic behavior, this paper proposes a physical model that employs tungsten trioxide (WO3), nickel oxide (NiO) and LiClO4-propylene carbonate (PC) solution. Within electrochromic films, electrolytes can transport lithium ions and anions through porous layers of electrochromic films. At the interfaces between solution and porous layers, lithium-ion intercalation and deintercalation take place. Considering both ion diffusion and electromigration, ion transport kinetics is described by Nernst-Plank equation. The partial differential equations (PDEs) for potential consist of Poisson equations for electrolytes and Ohm’s law for WO3 and NiO films. Moreover, the ion injection behavior at the interface is governed by Frumkin-Butler-Volmer (FBV) equation and potential conditions of the stern layer. Finally, a modified Beer–Lambert law incorporating porosity is proposed to explain the mechanism of transmittance. Under constant step potential conditions, the state variables of multiphysics field can be tracked, and the dynamic process of the transmittance and electrode current can be accurately predicted. This physical model can be applied for parameter design and precise control of ECDs, based on the optimization of device characteristics.

Controls on the Salinity of Sedimentary Basinal Fluids Under Constant Chemogravitational Potential Conditions

AbstractFluids in sedimentary basins exert a crucial influence on various geological phenomena including natural resource formation. Worldwide drilling projects have revealed that the salinity of sedimentary basinal fluids generally increases with depth, irrespective of lithology, age of sediments, or the presence of a halite bed. However, how these vertical salinity variations are produced and what controls the salinity remain unclear. This work examines a new hypothesis that downward‐increasing salinity variations are a natural outcome of the constant chemogravitational potential condition. In a static environment, the salinity is distributed such that the chemogravitational potential of the solute is constant with depth. Once formed, such a distribution would be maintained because no further migration of the solute would occur. To test the hypothesis, a constant chemogravitational potential distribution model was constructed for NaCl–H2O fluids in the sediment column, and NaCl content at each depth was calculated. The results showed that NaCl content monotonically increases with depth, and the variations are similar to the trend of measured data. However, the data were not necessarily completely reproduced by the model, and deviated in some parts from the calculated profile. Such deviation may indicate fluxing of external fluid occurring in these parts, as the constant chemogravitational potential is vulnerable to an advective flow. Therefore, it is proposed that the constant chemogravitational potential condition is a possible endmember theory, influencing natural salinity variations in a static environment.

Simulations of phase transitions and capacitance, of simple ionic fluids in porous electrodes

In this work, we simulate the capacitance of a simple charged fluid model consisting of equal-sized, spherical monovalent ions, immersed in an implicit solvent. Apart from Coulomb forces, the particles interact via a truncated and shifted Lennard-Jones potential. This is a possible crude model for hydrophobic ions (assuming an implicit aqueous solvent) and allows for a possible demixing transition in the solution. Such a phase separation may be driven by charging a narrow slit-like pore, immersed in a dilute (“gas-like”) bulk phase, akin to a capillary condensation. We highlight the dramatic effect that boundary conditions and regulatory control have on electrical properties (e.g., the differential capacitance) at the point of transition. For example, the surface potential displays a vertical (first-order) transition, as a function of surface charge density, when the latter is constrained to be uniform over the pore surfaces. At short separations, the transition is gradual (i.e., not first-order), which leads to a regime with an apparent ”non-physical” negative differential capacitance. Under conditions of constant surface potential, the negative capacitance region becomes inaccessible, as a first-order (horizontal) transition is reasserted. This is true for both conducting and non-conducting surfaces.

Synthesis and optimization of Mo–Ni–Se@NiSe core-shell nanostructures as efficient and durable electrocatalyst for hydrogen evolution reaction in alkaline media

Synthesis conditions are among the most influential factors in the electrocatalytic properties of the samples studied for the hydrogen evolution reaction (HER). In this study, conditions of NiSe synthesis over a Mo–Ni–Se layer were optimized to create core-shell nanostructures with excellent electrocatalytic properties. To optimize the synthesis conditions, first, two electrodeposition techniques in constant potential and pulse potential conditions were investigated and then the optimal temperature for electrodeposition between 5, 25, 40, and 60 °C was found. The electrocatalytic activity of the synthesized samples was investigated using linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry tests in a 1 M KOH solution. Preliminary results showed that pulsed electrodeposition of NiSe could improve the electrocatalytic activity of Mo–Ni–Se by forming durable and suitable nanostructures, while electrodeposited NiSe at constant potential could reduce the electrocatalytic activity of the electrode by forming a dense structure. Then, to determine the appropriate temperature, electrodeposition at the optimal pulse potential at four temperatures of 5, 25, 40, and 60 °C was used to synthesize NiSe on Mo–Ni–Se. The final results showed that the sample synthesized at 60 °C with an electrochemically active surface area of 2870 cm2 had the highest hydrogen production sites and required only an overpotential of 77 mV to achieve a current density of 10 mA cm−2.

Simple and Scalable Cathodic Synthesis of 1H-1-Hydroxyquninolin-4-ons and 4H-4-Hydroxy-1,2,4-benzothiadiazine-1,1-dioxides

Cathodic synthesis is a highly attractive technique for N,O bond reduction.[1] Especially, electro-reductions of nitro arenes enable the access to high-valuable products like nitrones and N-heterocycles.[2] These substances are in general unique structural motifs in natural products or in compounds with significant biological properties, such as antibiotic, antiplasmodial, antimycotic, antihypertensive, hyperglycemic and cytotoxic activities.[3] Commonly used synthesis methods require large amounts of metallic reducing agents, expensive transition metal catalysts, or hazardous oxidizers in case the corresponding heterocycles are accessible otherwise.[4] Several examples have been described with constant potential conditions using mercury or sacrificial lead electrodes.[5] Due to cathodic corrosion of heavy metals, this proves to be a critical aspect and mercury is banned in the most countries for technical applications.[6] Therefore, the urge for more sustainable processes is of high focus.We describe an access to 1H-1-hydroxyquninolin-4-ons by cathodic reaction of nitrobenzoyl acetones synthesized from broad available nitrobenzoic acids. Using metal-free BDD cathodes (boron-doped diamond), sulfuric acid as a simple supporting electrolyte, in addition to an aqueous electrolyte system with an environmentally benign co-solvent agree with sustainable and green aspects. The scalability under constant current conditions in an undivided cell has been shown in a twentyfold scale. The electrochemical synthesis protocol was applied to 18 examples including the antibiotic substance HQNO (1H-2-heptyl-1-hydroxy quinolin-4-ons) and various precursors for enzymatic aurachine synthesis.[7] Furthermore, we developed a method to a novel substance class of 4H-4-hydroxy-1,2,4-benzothiadiazine-1,1-dioxides. Reduction of the nitro precursors applying BDD cathodes result in hydroxylamines using divided cells with glass frits as separators. The applicability of this electro-reductive cyclisation is demonstrated by the synthesis of a broad product scope with activated, deactivated, labile and sterically demanding substitution patterns for potential further modification towards pharmaceutical applications.[8] Particularly, we described the synthesis of the N-Hydroxy analogues of diazoxide, a medication on the WHO list of essential medicines.[8,9] Studies on the biological activities of these new compounds are currently performed.

Electrochemically Catalyzed N–N Coupling and Ring Cleavage Reaction of 1H-Pyrazoles

AbstractThe electrocatalyzed N–N coupling and ring cleavage reaction of 3-methyl-, 3,5-dimethyl-, 3-methyl-5-phenyl- and 3,5-diphenyl-1H-pyrazole was investigated and led to the electro-organic synthesis of new heterocyclic compounds. The results revealed that electrochemically produced 1H-pyrazoleox plays the role of acceptor in a reaction with the starting molecule via a N–N coupling and ring cleavage reaction of pyrazoles. The proposed reaction sequence consists of anodic oxidation, dimerization, rearrangement and reduction. The electrochemically catalyzed reactions were accomplished under constant-current and constant-potential conditions using an undivided electrochemical cell with the advantages of mild reaction conditions, remarkable yields and environmental compatibility.

Reconciling the Experimental and Computational Hydrogen Evolution Activities of Pt(111) through DFT-Based Constrained MD Simulations

The computational hydrogen evolution activity of Pt(111) remains controversial due to apparent discrepancies with experiments concerning rate-determining activation free energies and equilibrium hydrogen coverages. A fundamental source of error may lie within the static representations of the metal–water interface commonly employed in density functional theory (DFT)-based kinetic models neglecting important entropic effects on reaction dynamics. In this work, we present a dynamic reassessment of the Volmer–Tafel hydrogen evolution pathway on Pt(111) through DFT-based constrained molecular dynamics simulations and thermodynamic integration. Hydrogen coverage effects are gauged at two distinct surface saturations, while the critical potential dependence and constant potential conditions are accounted for using a capacitive model of the electrified interface. The uncertainty in the highly nontrivial treatment of the electrode potential is carefully examined, and we provide a quantitative estimation of the error associated with dynamically simulated electrochemical barriers. The dynamic description of the electrochemical interface promotes a substantial decrease of the Tafel free energy barrier as the coverage is increased to a full monolayer. This follows from a decreased entropic barrier due to suppressed adlayer dynamics compared to the unsaturated surface, a detail easily missed by static calculations predicting notably higher barriers at the same coverage. Due to observed endergonic adsorption of active hydrogen intermediates, the Tafel step remains rate-determining irrespective of the coverage as illustrated by composed Volmer–Tafel free energy landscapes. Importantly, our explicitly dynamic approach avoids the ambiguous choice of frozen solvent configuration, decreasing the reliance on error cancellation and paving the way for less biased electrochemical simulations.

Controlling potential difference between electrodes based on self-consistent-charge density functional tight binding.

A proper understanding and description of the electronic response of the electrode surfaces in electrochemical systems are quite important because the interactions between the electrode surface and electrolyte give rise to unique and useful interfacial properties. Atomistic modeling of the electrodes requires not only an accurate description of the electronic response under a constant-potential condition but also computational efficiency in order to deal with systems large enough to investigate the interfacial electrolyte structures. We thus develop a self-consistent-charge density functional tight binding based method to model a pair of electrodes in electrochemical cells under the constant-potential condition. The method is more efficient than the (ab initio) density functional theory calculations so that it can treat systems as large as those studied in classical atomistic simulations. It can also describe the electronic response of electrodes quantum mechanically and more accurately than the classical counterparts. The constant-potential condition is introduced through a Legendre transformation of the electronic energy with respect to the difference in the number of electrons in the two electrodes and their electrochemical potential difference, through which the Kohn-Sham equations for each electrode are variationally derived. The method is applied to platinum electrodes faced parallel to each other under an applied voltage. The electronic response to the voltage and a charged particle is compared with the result of a classical constant-potential method based on the chemical potential equalization principle.

Towards constant potential modeling of CO-CO coupling at liquid water-Cu(1 0 0) interfaces

We use density functional theory, molecular dynamics, and metadynamics to study electrochemical *CO–*CO coupling in explicit electrolyte. We consider both the *CO–*CO coupling reaction and the charging process required to keep the potential constant. The charging process consists of transferring explicit cations from the electrolyte and electrons from the potentiostat to the interface. Under constant charge conditions (non-constant electrostatic potential), the *CO–*CO coupling reaction energies are relative insensitive to the charge state at the interface and the electrolyte composition and the reaction occurs with co-adsorption of water. Under constant potential conditions, the *CO–*CO coupling reaction is stabilized at lower potentials because of charging, the reaction is influenced by the electrolyte composition, and water-coadsorption is reduced. The *CO–*CO coupling reaction changes the electrosorption valency by around 0.4–0.5. We propose a simple approach to convert energetics from constant charge to estimates at constant potential. The approach is generally applicable to electrochemical processes.

Interaction between Charge-Regulated Metal Nanoparticles in an Electrolyte Solution

We present a theory which allows us to calculate the interaction potential between charge-regulated metal nanoparticles inside an acid-electrolyte solution. The approach is based on the recently introduced model of charge regulation which permits us to explicitly-within a specific microscopic model-relate the bulk association constant of a weak acid to the surface association constant for the same weak acid adsorption sites. When considering metal nanoparticles we explicitly account for the effect of the induced surface charge in the conducting core. To explore the accuracy of the approximations, we compare the ionic density profiles of an isolated charge-regulated metal nanoparticle with explicit Monte Carlo simulations of the same model. Once the accuracy of the theoretical approach is established, we proceed to calculate the interaction force between two charge-regulated metal nanoparticles by numerically solving the Poisson-Boltzmann equation with charge regulation boundary condition. The force is then calculated by integrating the electroosmotic stress tensor. We find that for metal nanoparticles the charge regulation boundary condition can be well approximated by the constant surface charge boundary condition, for which a very accurate Derjaguin-like approximation was recently introduced. On the other hand, a constant surface potential boundary condition often used in colloidal literature, shows a significant deviation from the charge regulation boundary condition for particles with large charge asymmetry.

Molecular Mechanism of Gas Solubility in Liquid: Constant Chemical Potential Molecular Dynamics Simulations.

Accurate prediction of gas solubility in a liquid is crucial in many areas of chemistry, and a detailed understanding of the molecular mechanism of the gas solvation continues to be an active area of research. Here, we extend the idea of the constant chemical potential molecular dynamics (CμMD) approach to the calculation of the gas solubility in the liquid under constant gas chemical potential conditions. As a representative example, we utilize this method to calculate the isothermal solubility of carbon dioxide in water. Additionally, we provide microscopic insight into the mechanism of solvation that preferentially occurs in areas of the surface where the hydrogen network is broken.

Measuring slow heteroaggregation rates in the presence of fast homoaggregation

Homoaggregation and heteroaggregation involving amidine and sulfate latex particles in the presence of the anionic surfactant octyl sulfate (OS) is studied by light scattering. This surfactant causes a charge reversal of the amidine particles. This reversal induces a rapid homoaggregation near the charge reversal point. In the presence of the same surfactant, the sulfate particles remain negatively charged and stable. The heteroaggregation process is probed in mixed suspensions of amidine and sulfate latex particles with multi-angle time-resolved dynamic light scattering. This technique allows differentiating between the contributions of homoaggregation and heteroaggregation, and permits to measure the heteroaggregation rate. By optimally choosing the sizes of the particles, one can optimize the contrast and extract heteroaggregation stability ratio over a wide range. The heteroaggregation rate is fast at low OS concentrations, where the two particles are oppositely charged. This rate slows down at higher OS concentrations due to double layer repulsion between the negatively charged particles. However, the onset of this slow heteroaggregation occurs at lower OS concentrations than for homoaggregation. The reason for this shift is that the double layer repulsion between two OS-decorated amidine particles is weaker than between one sulfate particle and one OS-decorated amidine particle. These measurements compare favorably with calculations with the theory by Derjaguin, Landau, Verwey, and Overbeek (DLVO). These calculations suggest that constant potential boundary conditions are more appropriate than the ones of constant charge. In the system studied, the present light scattering technique permits to extract heteroaggregation stability ratios over almost three orders of magnitude. This study is the first of its kind, where such a large range is being probed.

Preferential Interaction of Chymotrypsinogen in Aqueous Solutions of Polyols at 298.15 K

Preferential interactions of α-chymotrypsinogen in water and aqueous solutions of ethylene glycol, glycerol, erythritol, sorbitol, and inositol were studied from precise density measurements under conditions of constant molality and constant chemical potential; to achieve the last condition, solutions were brought under equilibrium dialysis. The density measurements were performed at 298.15 K and they were used to determine the preferential interaction parameters. The results confirm a significant correlation between the numbers of hydroxyl groups of the polyols with the stability of α-chymotrypsinogen.

Structural, electronic and magnetic properties of Mn doped ZnO nanoplates synthesized by electrodeposition method

The electronic, crystallographic and magnetic properties of ZnO thin films doped with manganese (Mn) agent were studied at various Mn concentrations. The samples were prepared electrochemically, under constant electric potential conditions. All Zn1−xMnxO (x = 1, 3, 5, 7 and 10%) samples exhibit typical wurtzite crystal structure with strong (002) orientation. The grains of samples are well-shaped and highly oriented nanoplates observed from SEM measurements. There is a strong correlation between the magnetic properties and electronic structure for all samples. The XPS analysis data revealed that Mn atoms are in oxidized state rather than metallic state. In addition, electron donation from Mn to Zn has changed the electronic structure of host lattice. The magnetic properties of samples are investigated by sweeping temperature and magnetic field. It is revealed that the antiferromagnetic interactions increases with Mn content in ZnO host lattice which is addressed by the formation of Mn-O-Mn bonding from the XPS data.

Constant Potential, Electrochemically Active Boundary Conditions for Electrochemical Simulation

In this manuscript, we present a model for simulating active electrochemical systems using a classical molecular dynamics framework. We describe a computationally efficient method of enforcing the electrostatic properties of constant potential boundary conditions and demonstrate how this method can be adapted to support stochastic interfacial charge-transfer processes. We highlight the utility of this model by simulating the nonequilibrium dynamics of a model battery system. We demonstrate the ability of this model to support the formation of a stable double structure, consistent with expectations from macroscopic equilibrium. We also illustrate how this model can be used to provide microscopic physical insight into the results of standard potential-jump experiments.

Efficient Three-Component One-Pot Synthesis of 4H-Pyrans

Clean, practical, and efficient electrochemical synthesis of pharmaceutically relevant 4H-pyran derivatives by one-pot three-component combination of an aryl aldehyde, malononitrile, and a dicarbonyl compoundis developed. The synthesis is performed in ethanol with lithium perchlorate as a supporting electrolyte in an undivided cell on a platinum electrode under constant potential electrolysis conditions.