Anodic Coupling Research Articles

Microbial electrochemical driven anaerobic ammonium oxidation coupling to denitrification in a single-chamber stainless steel reactor for simultaneous nitrogen and carbon removal

Anodic ammonium oxidation mainly focuses on autotrophic process, and the removal combined with organic matter oxidation is still unclear in microbial electrolysis cell (MEC). Here, a stainless-steel tank is constructed as an MEC for anaerobic ammonium oxidation and organic matter removal. Results show that MEC increases ammonium oxidation from 3.83 ± 2.51% to 32.90 ± 3.39%, and the organic matter removal rises from 75.69 ± 0.59% to 92.12 ± 0.57%, and the energy consumption is only 0.80 ± 0.09 kWh kg−1N, indicating an energy-efficient approach for simultaneous ammonium and carbon removal. Cyclic voltammetry reveals two pairs of oxidative peaks (−0.4 V and + 0.6 V) which demonstrate the electrochemical activity of biofilms for organic matter and ammonium oxidation, respectively. 16S rRNA gene analysis clarifies the anodic biofilm mainly enriched by the genus of Azoarcus, Hydrogenophaga and Paracoccus. Further analysis indicates that anodic potential controls the community succession of heterotrophic and hydrogenotrophic denitrifying bacteria, and then regulates the nitrogen and carbon removal processes, which extend the insights of anodic anaerobic ammonium oxidation coupling to denitrification under organic conditions.

A Flow Electrochemical Cell with Split Bipolar Electrode for Anodic Oxidation of Organic Compounds

AbstractThe recent development of flow electrochemical reactors has been remarkable, but efforts are still required to reduce the amount of supporting electrolyte used in electrosynthesis. To address this problem, herein an advanced process combining flow reactors and bipolar electrochemistry is proposed. The developed electrochemical system was successfully employed for the anodic fluorination and anodic coupling of organic compounds using low concentration of supporting electrolytes. Such combined electrochemical system would represent a promising electrosynthesis method toward green and sustainable chemistry.

Ultrastable sodium metal plating/striping by engineering heterogeneous nucleation on TiO2 nanotube arrays

• 3D spaced TiO 2 nanotube arrays (STNTs) were coated with ultra-fine metal nanocrystals. • We propose an absorption-diffusion regulation strategy to regulate Na deposition. • AIMD simulations demonstrate a mixed Na-Ag layer at the interface. • STNTs-Ag||Na displays a high Coulombic efficiency ∼99.5% even after 500 cycles. • STNTs-Ag-Na exhibits an ultralow overpotential of 4 mV and long cycling life over 1400 h. Sodium metal is considered as an excellent anode material for sodium-based energy storage devices with both high energy density and low cost, but the uncontrollable growth of sodium metal seriously limits its application. Herein, we firstly propose 3D spaced TiO 2 nanotube arrays (STNTs) uniformly coated with ultra-fine metal (Ag, Cu) nanocrystals as a substrate with absorption-diffusion regulation strategy to control the sodium metal deposition behavior. TiO 2 has a higher sodiophilic activity with larger Na absorption energy than the traditional copper substrate. Moreover, it is found by ab initio molecular dynamics (AIMD) simulations that it is much easier for Na to spread upon the surface of silver compared to copper, and thus forming a mixed Na-Ag layer at the interface. As a result, sodium metal is inclined to deposit inside or along the nanotube in STNTs-Ag in nanoscale. Finally, STNTs-Ag||Na half-cell displays a high Coulombic efficiency ∼99.5% even after 500 cycles with 1 mAh cm −2 . Symmetric cell of STNTs-Ag-Na exhibits an ultralow overpotential of 4 mV and a long-term cycling life over 1400 h. Moreover, STNTs-Ag-Na anode coupling with Na 3 V 2 (PO 4 ) 3 cathode exhibits a significantly reduced polarization voltage with 22 mV and improved rate performance with 110 mAhg −1 at 10 C.

Modern Synthesis and Chemistry of Stabilized Ketene N,O-Acetals

AbstractKetene N,O-acetals are robust and versatile synthons. Herein, we outline the synthesis of stable ketene N,O-acetals in the twenty-first century. In addition, we review recent developments in the chemistry of ketene N,O-acetals, as it applies to the vinylogous Mukaiyama aldol reaction, electrolysis, and pericyclic transformations. While dated reports rely on in situ use, modern methods of ketene N,O-acetal synthesis are heavily oriented towards producing products with high ‘bench’ stability; moreover, in the present century, chemists typically enhance the stability of ketene N,O-acetals by positioning an electron-withdrawing group at the β-terminus or at the N-position. As propitious substrates in the vinylogous Mukaiyama aldol reaction, ketene N,O-acetals readily provide polyketide adducts with high regioselectivity. When exposed to electrolysis conditions, the title functional group forms a reactive radical cation and cleanly couples with a variety of activated olefins. Given their electron-rich nature, ketene N,O-acetals act as facile substrates in several rearrangement reactions; further, ketene N,O-acetals reserve the ability to act as either dienophiles or dienes in Diels–Alder reactions. Lastly, ketene N,O-acetals are seemingly more stable than their O,O-counterparts and more reactive than analogous N,N- or S,S-acetals; these factors, in combination, make ketene N,O-acetals advantageous substitutes for other ketene acetal homologues.1 Introduction2 Select Methods of Stabilization-Oriented Ketene N,O-Acetal Synthesis3 Ketene N,O-Acetals in the Vinylogous Mukaiyama Aldol Reaction4 Ketene N,O-Acetals in Anodic Coupling and Electrochemical Oxidation Reactions5 Rearrangement and Diels–Alder Reactions of Ketene N,O-Acetals6 Conclusions, Perspectives, and Directions

Biomimetic total synthesis of (-)-galanthamine via intramolecular anodic aryl-phenol coupling.

(-)-Galanthamine as a drug for the treatment of Alzheimer's disease has attracted synthetic chemists for decades. However, previous total synthetic and biomimetic approaches often use stoichiometric oxidants (metal oxidants or hypervalent iodine) to prepare the target product. Anodic oxidative coupling offers a sustainable alternative method which is, for the first time, successfully applied to the total synthesis of (-)-galanthamine. We report a new asymmetric total synthesis of (-)-galanthamine by using an anodic aryl-phenol coupling as the key synthetic step.

EQCM Analysis of the Insertion Phenomena in a n-Doped Poly-Alkyl-Terthiophene With Regioregular Pattern of Substitution.

In the present work, we have undertaken the study of the n-doping process in poly-3,3″-didodecyl-2,2′:5′,2″-terthiophene (poly-33″-DDTT) employing the electrochemical quartz crystal microbalance (EQCM). The present study aims at understanding how cathodic charge in n-doped poly-33″-DDTT is compensated. For this purpose, the in situ analysis of the variations of the polymeric mass has been considered. Poly-33″-DDTT was obtained as a thin coating onto a metallic substrate via the anodic coupling of the corresponding monomer 3,3″-didodecyl-2,2′:5′,2″-terthiophene (33″-DDTT). When subjected to electrochemical n-doping in the polarization interval -2.5 ≤ E appl ≤ 0 V vs. Ag/Ag+, the films of poly-33″-DDTT varied their mass according to a mechanism of cations insertion during n-doping and cations extraction during polymer neutralization. In fact, the electrochemical doping of polythiophenes requires the accompanying exchange of charged species to maintain the electroneutrality within the structure of the polymer in all states of polarization. At the end of a full electrochemical cycle (consisting of the n-doping and the successive neutralization of poly-33″-DDTT), the polymer retains a fraction of the mass acquired during n-doping, thus manifesting the phenomena of mass trapping. The combined analysis of electrochemical and microgravimetric data suggests that poly-33″-DDTT in the n-doped state undergoes (or electrocatalyzes) uncontrolled electrochemical reactions that are not accompanied by mass variations.

All‐Climate Iron‐Based Sodium‐Ion Full Cell for Energy Storage

AbstractThe anode materials for sodium‐ion batteries (SIBs) such as soft carbon, hard carbon, or alloys suffer from low specific capacity, poor rate capability, and high cost. Various transition metal oxides materials possess high specific capacity and suitable working potential, however, huge volume change and unstable electrode/electrolyte interfaces limit their practical applications. Herein, an ultrathin carbon‐coated iron‐based borate, (Fe3BO5), as an anode material for SIBs is reported. The carbon coated Fe3BO5 composite as an anode material possesses a reversible specific capacity of 548 mAh g−1 with a high initial coulombic efficiency of 72.6% at a current density of 50 mA g−1, and maintains a capacity retention ratio of 99% after 1000 cycles at 2000 mA g−1. Moreover, this anode can work well over a wide temperature range (‐40–60 °C). Furthermore, a sodium‐ion full cell using this anode coupling with iron‐based cathode (Na3Fe2(PO4)2(P2O7)@rGO) cathode is fabricated, which exhibits a wide operating temperature range from −40 to 60 °C with a maximum energy density of 175 Wh Kg−1 and a maximum power density of 1680 W Kg−1. Most importantly, this full‐cell configuration is low‐cost due to its inexpensive iron based raw material for both anode and cathode.

Anodic Olefin Coupling Reactions: Elucidating Radical Cation Mechanisms and the Interplay between Cyclization and Second Oxidation Steps.

Anodic olefin coupling reactions generate new bonds and ring skeletons through a net two electron process that reverses the polarity of a known, electron-rich functional group. While much of the early work on the mechanism of these reactions focused on the initial oxidation and cyclization steps of the process, the second oxidation step also plays a central role in determining the success of the reaction. Evidence supporting this observation is presented, along with evidence that optimization of this second oxidation step is not enough to pull a poor cyclization to the desired product. Successful cyclization reactions require optimization of both processes.

Rechargeable aqueous aluminum-FeFe(CN)6 battery with artificial interphase through deep eutectic solution

The application needs of small electronic devices and large-scale power grid storage continuously promote the development of a new battery energy system. Rechargeable metal batteries based on aluminum (Al) are of enormous potential due to the abundant Al reserves, the trivalent charge carrier, high theoretical specific capacity (2980 mAh/g), and volumetric energy density (8046 mAh/cm3). However, the passivating oxide layer on the surface of the Al anode blocks the migration of electrons and ions, resulting in the operation difficulty and irreversibility of aluminum-based batteries. Herein we treated Al anode with a deep eutectic solution (DES) and constructed stable solid interface interphase on its surface, which can effectively prevent surface passivation, improve the chemical properties of the interface, promote ion transfer, and enable aqueous Al batteries with superior electrochemical performance. The assembled symmetric cells with treat Al (TAl) can cycle for more than 300 h with a low overpotential (~0.2 V). The TAl anode coupling with the FPB cathode material to assemble the full cells based on the aqueous electrolyte system can deliver a high discharge capacity of 85 mAh/g and exhibit capacity retention of 58 mAh/g after 150 cycles and an average coulombic efficiency of 97.1% at a current density of 100 mA/g. This work provides a novel surface modification strategy of Al metal anode and demonstrates high stability and cost-effective aqueous Al metal battery system, which suggest the significance for the commercialization of Al-metal batteries and their applications in large-scale energy store.

Comparison between Ar+CH4 cathode and anode coupling chemical vapor depositions of hydrogenated amorphous carbon films

This research focuses on the comparison between cathode- and anode coupling deposition characteristics of hydrogenated amorphous carbon (a-C:H) using the capacitively coupled plasma (CCP) method. a-C:H films were fabricated by Ar+CH4 CCP chemical vapor deposition. The cathode and anode coupling depositions were simultaneously performed in a single CCP reactor. Compared to the anode coupling process, the cathode coupling process provides high-kinetic-energy ions impinging on the film surface. The cathode coupling process produced a-C:H films with a mass density of 1.75 g/cm3 and a hydrogen content of 36% at a deposition rate of 22.9 nm/min. By contrast, the anode coupling process resulted in a-C:H films with a mass density of 1.4 g/cm3 and a hydrogen content of 50% at a deposition rate of 10 nm/min. Raman spectroscopy shows that a-C:H films in the cathode coupling process have a highly disordered bonding, whereas a-C:H films in the anode coupling process have highly strained graphite.

Ultrasmall Mo2C nanocrystals embedded in N-doped porous carbons as a surface-dominated capacitive anode for lithium-ion capacitors.

In situ uniform confinement of ultrasmall Mo2C nanocrystals into micropore-enriched N-doped carbons was achieved by carbonizing phosphomolybdic acid/polyimide precursors to craft a surface-dominated capacitive battery-type anode. Upon coupling with a capacitor-type cathode, the as-fabricated lithium-ion capacitors exhibit superior power and energy outputs by improving the kinetics and capacity imbalance between two electrodes.

Highly concentrated nitrile functionalized disiloxane - LiFSI based non-flammable electrolyte for high energy density Li metal battery

Abstract High energy density and safety are key issues of Li metal battery (LMB). A thin Li anode coupling with high voltage/high capacity cathode (NCM811) can increase the energy density of Lithium batteries. We have developed a fire retardant disiloxane based highly concentrated electrolyte which makes a coordinated Li+-FSI−-Solvent cluster to produce stable interphase on electrodes. This electrolyte shows reduced reactivity towards Li metal anode. The oxidation stability of electrolyte is high (5 V) and also shows less Al corrosion. The synergistic effect of additive makes inorganic ‘LiF’-rich dendrite free interphase. SEM analysis confirms dendrite free surface morphology. A Li metal full cell is fabricated with thin Li anode (20 μm, 4.12 mAh/cm2) and NCM811 cathode with moderate active material loading (1.1 mAh/cm2), providing a high energy density of 614 Wh kg−1 (based on total weight of anode and cathode excluding current collectors).

Electrodeposited thiophene-containing organic small molecule-modified ITO electrode with highly efficient photoelectric conversion and photoelectrochemical oxygen reduction

An organic small molecule-based thin film on an indium-tin oxide (ITO) electrode was fabricated by anodic coupling of a novel thiophene unit-capping organic small molecule (L), and characterized by ultraviolet-visible absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and photoelectrochemical measurements. The n cycles of anodic potential scanning produced red-colored electrodeposited films of Film(dimer-Ln) in minutes with visible light harvesting characteristics akin to those previously observed for ruthenium polypyridyl complex star dye-based films that were much more costly and difficultly accessible. Film(dimer-Ln) films were found to exhibit surface-controlled thiophene unit associated redox behaviors and significant cathodic photocurrent generation properties. As irradiated with white light at 100 mW cm−2 and biased at a zero potential, a Film(dimer-L2)-modified ITO electrod exhibited a high photo-to-current conversion efficiency of 0.90% at 450 nm, and a photocurrent density of 13.6 μA cm−2 in an N2-saturated electrolyte solution, which was greatly boosted by ~7 folds to 108.8 μA cm−2 in an O2-saturated electrolyte solution. The resulting modified electrodes offer great prospects for a wide range of applications ranging from photoelectric conversion to light detection devices to photoelectrocatalytic O2 reduction and sensing.

Electrosynthesis 2.0 in 1,1,1,3,3,3‐Hexafluoroisopropanol/Amine Mixtures

AbstractThe intention of this review is to highlight the innovative electrolyte combination of 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) with tertiary nitrogen bases in electro‐organic synthesis. This easy applicable and promising mixture is not yet well established in electro‐organic synthesis, but expands the various possibilities in the latter. Combinations of fluorinated alcohols with nitrogen bases form highly conductive electrolyte systems, which can be evaporated completely. Consequently, no additional supporting electrolyte is required and work‐up procedures are tremendously simplified. With this electrolyte mixture carbon‐carbon homo‐ and cross‐coupling reactions of arenes and phenols have been established with substrates that have not been previously susceptible to the anodic dehydrogenative coupling reaction. The intermediate installation of highly fluorinated alkoxy moieties can be exploited for subsequent conversions as well as various benzylic functionalization, including asymmetric transformations. These transformations show unique selectivity and functional group tolerance making them highly applicable to the synthesis of sophisticated structural motifs, including natural products.

Outstandingly robust anodic dehydrogenative aniline coupling reaction

Oxidative treatment of anilines usually leads to the formation of black polymers, often referred to as “aniline black”. This over-oxidation is hardly controllable and also a challenging task in the anodic conversion of anilines. Here, a quick and efficient access to valuable building blocks by anodic cross- and homo-coupling of aniline and benzidine derivatives is reported. This electrosynthesis is easily performed in a simple undivided cell using constant current conditions. The key to the observed outstanding performance and robustness of this system is attributed to the used solvent 1,1,1,3,3,3-hexafluoroisopropanol. The extraordinary performance over a broad range of current density is unprecedented for reactions involving extremely oxidation labile substrates such as anilines and their derivatives.

Total Synthesis of (-)-Oxycodone via Anodic Aryl-Aryl Coupling.

A fully regio- and diastereoselective electrochemical 4a-2'-coupling of a 3',4',5'-trioxygenated laudanosine derivative enables the synthesis of the corresponding morphinandienone. This key intermediate is further transformed into (-)-oxycodone through conjugate nucleophilic substitution for E-ring closure and [4 + 2] cycloaddition with photogenerated singlet oxygen to accomplish diastereoselective hydroxylation at C-14. The anodic transformation provides high yields and can be performed under constant current conditions both in a simple undivided cell or in continuous flow.

Paired Electrochemical Reactions and the On‐Site Generation of a Chemical Reagent

AbstractWhile the majority of reported paired electrochemical reactions involve carefully matched cathodic and anodic reactions, the precise matching of half reactions in an electrolysis cell is not generally necessary. During a constant current electrolysis almost any oxidation and reduction reaction can be paired, and in the presented work we capitalize on this observation by examining the coupling of anodic oxidation reactions with the production of hydrogen gas for use as a reagent in remote, Pd‐catalyzed hydrogenation and hydrogenolysis reactions. To this end, an alcohol oxidation, an oxidative condensation, intramolecular anodic olefin coupling reactions, an amide oxidation, and a mediated oxidation were all shown to be compatible with the generation and use of hydrogen gas at the cathode. This pairing of an electrolysis reaction with the production of a chemical reagent or substrate has the potential to greatly expand the use of more energy efficient paired electrochemical reactions.

Paired Electrochemical Reactions and the On-Site Generation of a Chemical Reagent.

While the majority of reported paired electrochemical reactions involve carefully matched cathodic and anodic reactions, the precise matching of half reactions in an electrolysis cell is not generally necessary. During a constant current electrolysis almost any oxidation and reduction reaction can be paired, and in the presented work we capitalize on this observation by examining the coupling of anodic oxidation reactions with the production of hydrogen gas for use as a reagent in remote, Pd-catalyzed hydrogenation and hydrogenolysis reactions. To this end, an alcohol oxidation, an oxidative condensation, intramolecular anodic olefin coupling reactions, an amide oxidation, and a mediated oxidation were all shown to be compatible with the generation and use of hydrogen gas at the cathode. This pairing of an electrolysis reaction with the production of a chemical reagent or substrate has the potential to greatly expand the use of more energy efficient paired electrochemical reactions.

Mechanism and optimization of electrochemical system for simultaneous removal of nitrate and ammonia.

In this study, an electrochemical system was established for simultaneous harmless removal of nitrate and ammonia multiple contamination in an undivided single cell. Cyclic voltammetry was used to investigate the electrochemical cathode and anode coupling redox mechanism and concurring evolution of nitrate and ammonia. The cyclic voltammograms showed the cathodic reduction of nitrate to ammonia and nitrite, the chloride ion conversion to hypochlorite and hypochlorous acid, and the oxidation of ammonia to nitrogen gas and nitrate. A circular transformation process was formed in the electrochemical system and the final product was harmless nitrogen gas. The multiple nitrogen pollutants in the original contaminated system were gradually removed with the reaction predominantly produced harmless nitrogen gas. Response surface methodology was used to build mathematical models for optimizing the operating conditions. The optimum time, NaCl concentration, and current density were 85.38 min, 0.24 g/L, and 45.13 mA/cm2, respectively. Under the optimum conditions, the nitrate and ammonia concentrations in the treated solution were 9.17 and 0.00 mg/L, respectively.

A Regio‐ and Diastereoselective Anodic Aryl–Aryl Coupling in the Biomimetic Total Synthesis of (−)‐Thebaine

The biosynthesis of thebaine is based on the regioselective, intramolecular, oxidative coupling of (R)-reticuline. For decades, chemists have sought to mimic this coupling by using stoichiometric oxidants. However, all approaches to date have suffered from low yields or the formation of undesired regioisomers. Electrochemistry would represent a sustainable alternative in this respect but all attempts to accomplish an electrochemical synthesis of thebaine have failed so far. Herein, a regio- and diastereoselective anodic coupling of 3',4',5'-trioxygenated laudanosine derivatives is presented, which finally enables electrochemical access to (-)-thebaine.